Spring is in the air, and with it comes bright & zesty flavors, like the ones in this key lime cake! The moist white cake layers are filled with a sweet & tart key lime curd and enrobed in a silky swiss meringue buttercream. Each bite is a citrus lover's dream!
Celebrate spring in good taste with this delicious key lime cake! Tart and fresh key lime curd is spread between layers of moist, fluffy white cake with a hint of lime zest, and it's all topped with a gorgeous, classic swiss meringue buttercream. It's the perfect make-ahead dessert that will look beautiful in any setting: on your Easter table, at a spring birthday party, or any other special occasion!
For more spring recipes, try Coconut Key Lime Bars, Olive Oil Lemon Upside Down Cake, Glazed Orange Pound Cake, and Deep Dish Coconut Cream Pie.
Why you'll love this key lime cake
- Moist White Cake Layers: These key lime cake layers have a super moist and soft texture with a hint of key lime flavor from the zest added!
- Tart Key Lime Curd: Bright and tart key lime curd adds a vibrant, flavorful taste to this cake - basically making it key lime pie in cake form!
- Silky, Smooth Buttercream: This Swiss meringue buttercream is silky yet sturdy, making it perfect for holding up cake layers and piping into designs.
- Easy Make Ahead Recipe: These cake layers are easiest to frost when frozen, so you can bake the layers ahead of time and frost the cake day-of.
Ingredient Notes
- Key Limes: If you can't find key limes, you can use regular limes, too!
- Unsalted Butter: Use high quality European-style butter for best overall flavor.
- Cake Flour: Cake flour will make this cake perfectly soft, but if you're in a pinch you can use all-purpose flour.
- Eggs: Bring your eggs to room temperature quickly by placing them in a bowl of warm water for 10 minutes.
- Vanilla: Add a high quality vanilla extract for optimal flavor.
See recipe card for full information on ingredients and individual quantities.
Step by Step Instructions
Here are step by step photos and instructions on how to make this key lime cake recipe! For the full ingredient list and method, see the recipe card at the end of this post.
STEP 1: Mix sugar and zest. In the bowl of a stand mixer fitted with a paddle attachment, add the sugar and key lime zest. Rub them together with your fingers until it resembles wet sand and smells aromatic.
STEP 2: Add dry ingredients and butter. To the sugar, mix in the flour, baking powder, and salt. Cut up 5 ½ tablespoons of butter into small cubes and add to the flour mixture. Mix on low speed until it resembles wet sand.
STEP 3: Add wet ingredients. Add the oil, whole milk, and vanilla, and mix until just combined.
STEP 4: Whip egg whites. In a separate medium bowl, add the egg whites. Use an electric hand mixer to whip them until medium peaks form.
STEP 5: Fold in egg whites. Gently fold the whipped egg whites into the batter with a rubber spatula until just combined.
STEP 6: Divide batter. Divide the cake batter between the prepared round cake pans.
STEP 7: Bake and freeze. Bake for about 22-25 minutes or until the cakes start to pull away from the sides of the pans and a toothpick comes out clean. Immediately turn the cakes out onto a wire rack to cool completely. Once cool, wrap the cakes in plastic wrap and freeze to lock the moisture in until ready to decorate. (Frozen cake layers will be much easier to frost!)
STEP 8: Make key lime curd. In a medium or large mixing bowl, whisk together the egg yolks, sugar, cornstarch, and salt until smooth and light in color. Then, mix in the fresh lime juice until fully combined. In a medium saucepan over low-medium heat, melt the butter. Pour in the egg yolk, lime juice mixture, then turn the heat up to medium, and mix constantly with a rubber spatula for 3-4 minutes or until thickened and large bubbles form in the center. Immediately remove from heat. Pour the key lime curd through a fine mesh sieve into a bowl. Stir in the key lime zest, then transfer to a jar and chill for at least 1 hour or overnight.
STEP 9: Make the Swiss meringue. Add the egg whites, sugar, and salt to the bowl and whisk until fully combined. Place over a small saucepan of simmering water, and whisk frequently until it reaches 160 degrees F. Move the bowl over to the stand mixer with the whisk attachment. Whisk on medium-high speed until medium peaks form. Add the vanilla and continue whisking until stiff peaks form. Turn the mixer down to low speed, and wait until the meringue cools down to at least 85 degrees F.
STEP 10: Add the butter. Cut the butter into cubes and add to the meringue a few pieces at a time, allowing them to fully incorporate before adding more. Once all of the butter is added, it may look curdled, but keep beating for a few more minutes and it will come together. Once the buttercream has mostly come together, change the whisk attachment to the paddle and keep mixing on low speed until homogenous and smooth.
STEP 11: Assemble cake. Place the first cake layer on a cake stand. Pipe a dam of buttercream around the edge of the cake. Fill the center with an even layer of key lime curd. Top with the second cake layer and repeat.
STEP 12: Decorate. Add the last cake layer and top with a few scoops of buttercream. Use an offset spatula to smooth out the top, and spread the excess all over the sides. Continue decorating the cake as desired. Top with key lime zest, and enjoy!
Expert Baking Tips
- Do not over-whip the egg whites. Whip the egg whites only to medium peaks. As you can see above, the peaks droop slightly - this is what you're looking for. Whipping them to stiff peaks will make the egg whites too dry, causing them to deflate as they're folded into the batter.
- Use cake strips to create flat cake layers. Soak these wilton cake strips in ice water before starting the cake batter. Just before baking, wrap the cake strips around the pan. The cold temperature on the outside of the cake will prevent the edges from baking faster than the center, resulting in an evenly baked flat cake.
- Freeze the cake layers before decorating. Since this is such a moist cake, I highly recommend freezing the cake layers for at least two hours before decorating.
- Wait until meringue cools down before adding butter. It is SO important to wait until the meringue drops down to at least 85 degrees F or you will risk the butter melting and the whole thing turning into a big soupy mess.
- To create smooth sides when cake decorating... Run an offset spatula (or any cake decorating tool) under hot water, then wipe dry and use immediately to spread the frosting on the cake. The hot tool will help create smooth sides!
Recipe FAQs
The reverse creaming method is the process of beating room temperature butter into the dry ingredients. The fat coats the flour and inhibits the gluten from developing. With this method, the cake is sure to bake up flat without becoming too golden around the edges or on top. In contrast, the creaming method involves beating the sugar and butter together, which adds a lot of extra air into the batter.
Swiss meringue buttercream is a meringue based frosting made with the swiss method, which involves heating egg whites and sugar over a double boiler before whipping to stiff peaks. Butter and flavorings are then mixed into the meringue, creating an incredibly sturdy & buttery frosting compared to other buttercreams. It also has a much more balanced sweetness compared to American buttercreams or a tangy cream cheese frosting.
You likely have added the butter to the meringue too soon. DO NOT add the butter to the swiss meringue until it has cooled down to below 85 degrees F. I have made the mistake of adding it too soon, and the meringue ended up melting the butter and turned the whole thing into a soupy mess. If your meringue has reached stiff peaks before it is cool enough, turn the mixer down to low speed and keep it there until it reaches the right temperature.
Store slices of this key lime cake in an airtight container at room temperature or in the refrigerator for 3-5 days or in the freezer for up to 3 months.
Baking in Grams
All of the recipes on this blog are carefully developed with gram measurements so you can easily recreate them in your own kitchen with success. Volume measurements are extremely inaccurate and leave room for significant errors. Not all measuring cups are made equally, so your one cup of flour will be different from my one cup of flour. By providing precise measurements in grams (aside from minor ingredients, which are given in tsp/tbsp), you can make these recipes accurately and with less cleanup! All you need is this kitchen scale.
If this still isn't enough to convince you, I have provided volume measurements in the recipe card. If you are interested in understanding the conversions, this is the best conversion chart.
But trust me, once you try baking in grams you'll never turn back!
Happy baking! x
Other cake and cupcake recipes to try
If you tried this recipe, I'd love to know how it turned out for you! Leave a star rating & review below and post a picture (or video!) on Instagram and tag me so I can see your bakes! Not ready to make this recipe yet? Click the heart button on the right of your screen to save it for later 🙂
📖 Recipe
Key Lime Cake
Ingredients
For the cake layers:
- 162 g granulated sugar
- zest of 5 key limes
- 210 g cake flour
- 2 teaspoon baking powder
- ½ teaspoon salt
- 76 g unsalted butter room temp
- 50 g neutral oil
- 227 g whole milk room temp
- 2 teaspoon vanilla extract
- 2 egg whites
For the key lime curd:
- 3 egg yolks
- 100 g granulated sugar
- 10 g cornstarch
- ½ teaspoon kosher salt
- 100 g fresh key lime juice
- 35 g unsalted butter
- Zest of 5 key limes
For the swiss meringue buttercream:
- 145 g egg whites
- 300 g granulated sugar
- ½ teaspoon salt
- 2 teaspoon vanilla extract
- 340 g unsalted butter room temp
Instructions
For the cake layers:
- Preheat the oven to 350 degrees F. Grease and line three 6 inch cake pans with parchment paper.
- In the bowl of a stand mixer fitted with a paddle attachment, add the sugar and key lime zest. Rub them together with your fingers until it resembles wet sand and smells aromatic.
- To the sugar, mix in the flour, baking powder, and salt.
- Cut up the butter into small cubes and add to the dry ingredients. Mix on low speed until it resembles wet sand.
- Add the oil, whole milk, and vanilla, and mix until just combined.
- In a separate medium bowl, add the egg whites. Use an electric hand mixer to whip them until medium peaks form.
- Gently fold the whipped egg whites into the batter with a rubber spatula until just combined.
- Divide the cake batter between the prepared pans.
- Bake for about 22-25 minutes or until the cakes start to pull away from the sides of the pans. Immediately turn the cakes out onto a wire rack to cool completely.
- Once cool, wrap the cakes in plastic wrap and freeze until ready to decorate. (Frozen cake layers will be much easier to frost!)
For the key lime curd:
- In a medium bowl, whisk together the egg yolks, sugar, cornstarch, and salt until smooth and light in color. Then, mix in the key lime juice until fully combined.
- In a medium saucepan over low-medium heat, melt the butter.
- Pour in the egg yolk, lime juice mixture, then turn the heat up to medium, and mix constantly with a rubber spatula for 3-4 minutes or until thickened and large bubbles form in the center. Immediately remove from heat.
- Pour the key lime curd through a fine mesh sieve into a bowl. Stir in the key lime zest, then transfer to a jar and chill for at least 1 hour or overnight.
For the swiss meringue buttercream:
- Wipe the bowl of a stand mixer and whisk attachment down with white vinegar.
- Add the egg whites, sugar, and salt to the bowl and whisk until fully combined.
- Place over a small saucepan of simmering water, and whisk frequently until it reaches 160 degrees F or until the sugar is completely dissolved and the mixture no longer feels grainy.
- Move the bowl over to the stand mixer with the whisk attachment. Whisk on medium-high speed until medium peaks form.
- Add the vanilla and continue whisking until stiff peaks form.
- Turn the mixer down to low speed, and wait until the meringue cools down to at least 85 degrees F.
- Cut the butter into cubes and add to the meringue a few pieces at a time, allowing them to fully incorporate before adding more.
- Once all of the butter is added, it may look curdled, but keep beating for a few more minutes and it will come together.
- Once the buttercream has mostly come together, change the whisk attachment to the paddle and keep mixing on low speed until homogenous and smooth.
For assembly:
- Place the first cake layer on a cake stand. Pipe a dam of buttercream around the edge of the cake. Fill the center with an even layer of key lime curd.
- Top with the second cake layer and repeat.
- Add the last cake layer and top with a few scoops of buttercream. Use an offset spatula to smooth out the top, and spread the excess all over the sides.
- Continue decorating the cake as desired. Top with key lime zest, and enjoy!
Notes
- Do not over-whip the egg whites. Whip the egg whites only to medium peaks. As you can see above, the peaks droop slightly - this is what you're looking for. Whipping them to stiff peaks will make the egg whites too dry, causing them to deflate as they're folded into the batter.
- Use cake strips to create flat cake layers. Soak these wilton cake strips in ice water before starting the cake batter. Just before baking, wrap the cake strips around the pan. The cold temperature on the outside of the cake will prevent the edges from baking faster than the center, resulting in an evenly baked flat cake.
- Freeze the cake layers before decorating. Since this is such a moist cake, I highly recommend freezing the cake layers for at least two hours before decorating.
- Wait until meringue cools down before adding butter. It is SO important to wait until the meringue drops down to at least 85 degrees F or you will risk the butter melting and the whole thing turning into a big soupy mess.
- To create smooth sides when cake decorating... Run an offset spatula (or any cake decorating tool) under hot water, then wipe dry and use immediately to spread the frosting on the cake. The hot tool will help create smooth sides!
Nutrition
The post Key Lime Cake appeared first on Sloane's Table.
