Key Lime Pie Cake
I made you a cake!
Just kidding. I made my dad a cake. He had another birthday – which he insists on doing every year, like clockwork – so I decided to make him a cake. I’ve talked about how much he likes key lime pie before. This year I threw in a twist – I made him Key Lime Pie Cake.
This whole cake is built around one key component: the key lime curd. It’s just like this quick & easy lemon curd, but it’s made with key lime juice instead. Once done, it tastes just like the silky sweet and mouth puckering filling of a key lime pie. SO good.
All finished, the cake was lovely. My best cake frosting job to date, if I may toot my own horn. It’s made of two layers of light and tender lime-scented white cake, with a thick layer of key lime curd between them, then frosted with a smooth and rich lime Swiss Meringue Buttercream. To finished it off, I toasted some graham cracker crumbs for the outside because we all know it’s not key lime pie without a graham cracker crust.
I don’t make full layer cakes like this very often because they’re such a project and there usually aren’t enough people around to eat them. That, and the suspense of waiting until the first slice to see if it tastes good just about kills me. What if it’s awful and I’ve just served it to a whole group of people? Yikes.
That said… I think this cake was a success. It tasted good, it looked good, and everyone who ate it seemed pleased. However, I think there’s a few things I would do differently next time:
- When I put the cake together, I was concerned that the wallop of flavor from the key lime curd could be overpowering and too rich when combined with frosting, so I went a little light on the curd. After tasting the cake myself* and harassing everyone who ate it for their opinions, I think I could have used more curd. It was by far the best and most flavorful part of the cake.
- I only used two layers because I had to travel with the cake and I was afraid more layers would not hold up in transit. Next time If I don’t have to travel with the cake, I’d like to try halving each cake layer to make four layers total. That would make room for more curd too!
- By the time we ate the cake, it was a little dry. I think this was due to 3 things: I was careless with measuring and used a little too much flour; I overbaked the cake layers a bit; and the cake sat uncovered in the fridge for a few days before eating. I’ve used this cake recipe before and it wasn’t dry, so I am sure the recipe is not at fault. Next time, I might baste the cake layers with a lime simple syrup just to ensure it stays moist.
* I was sick with the plague (aka a nasty cold) when I tasted this cake, and as such I could barely taste anything. I’m basing my opinions on what little I could taste and what others said about how it tasted.
Key Lime Pie Cake
Printable Recipe (includes all sub-recipes)
Makes one 9-inch layer cake
This cake has several components, most of which can (and should) be made ahead. Final assembly will ideally take place the same day the cake is served, but the cake can be stored in the fridge for up to 2 days.
Prepare key lime curd according to directions below at least one day (up to 3 days) ahead.
Bake cake layers according to directions below. Cool completely before frosting.
Prepare the Lime Swiss Meringue Buttercream according to directions below.
To assemble, place one cake layer (top side up) on a cake plate or board. Place about 3/4 cup of buttercream in a piping bag with a large round tip. Pipe frosting around top edges of cake to create a border of frosting. Fill in center with 1/2 cup or more of Key Lime Curd. Place other cake layer (top side down) on top.
Spread of thin layer of buttercream over top and sides of cake to form a crumb coat. Refrigerate cake for 30 minutes to 1 hour.
Place 1/4 to 1/2 cup of frosting in a piping bag with a star tip. Spread the remaining frosting evenly over top and sides of the cake. Press Graham Cracker Crumble into sides of cake. Spread about 1/2 cup of Key Lime Curd over top of cake, leaving 1/2-inch border. Pipe stars around top edge border.
Key Lime Curd
Adapted from Gourmet
Makes about 3 cups
I made a large batch of curd not knowing how much I would end up needing for final cake assembly. As pictured and described above, I only needed half of the curd for the cake. However, if you plan to make your cake 4 layers you will probably need the whole batch.
This recipe is very easy, but the key is patience. You must cook the curd on LOW heat very slowly and you must whisk constantly. For reference, my electric stove burners range from 1 to 9. I cooked my curd on 3-4 for 10+ minutes.
1 1/2 cups granulated sugar
zest of 4 limes
1 cup Key Lime juice
4 large eggs
8 tablespoons unsalted butter, cut into tablespoon-sized pieces
Add all ingredients except butter to a saucepan over Low heat. Whisk to combine. Add butter. Continue whisking gently but constantly, heating slowly, until curd thickens and reaches 160°F on an instant read thermometer. Remove from heat.
For the smoothest curd, pour through a fine mesh strainer. Transfer to a storage container. Cover and refrigerate overnight before use. Curd keeps up to 1 week in the fridge.
Lime Scented White Cake
Adapted from Baking: From My Home to Yours by Dorie Greenspan
Makes 2 9-inch cakes
2 1/4 cups cake flour
1 tablespoon baking powder
1/2 teaspoon salt
1 1/4 cups buttermilk
4 large egg whites
1 tablespoon lime juice
1 1/2 cups sugar
zest of 1 lime
1 stick (8 tablespoons) unsalted butter, room temperature
1/2 teaspoon vanilla extract
Preheat oven to 350°F. Spray two 9-inch round cake pans with baking spray.
Whisk together cake flour, baking powder and salt in a small bowl. In a 2-cup measuring cup, first measure out buttermilk, the whisk in egg whites and lime juice.
In the bowl of a stand mixer, beat sugar and zest on low until fragrant, about 2 minutes. Add butter and beat until light and fluffy, about 3 minutes. Beat in vanilla extract. With the mixer on low, add 1/3 of the flour mixture, followed by 1/2 buttermilk mixture. Continue alternating dry and wet ingredients (ending with dry ingredients), beating just to incorporate each new addition. Once all ingredients are added, beat on medium speed for 2 minutes to aerate the batter.
Divide batter evenly between pans. Bake at 350°F for 30-35 minutes, or until toothpick in the center comes out clean. Cool in pans for 5 minutes, then invert cakes onto a cooling rack to cool completely.
Can be made ahead. If making ahead, wrap each layer tightly in plastic wrap and place in a zip top bag. Can be stored at room temperature for a day, or frozen for several weeks.
Graham Cracker Crumble
6 graham crackers
pinch of salt
2 Tablespoons brown sugar
4 Tablespoons unsalted butter, melted
Preheat over to 350°F. Line a baking sheet with a Silpat or parchment paper.
Break graham crackers into quarters and pulse in a food processor until reduced to fine crumbs. Add salt and brown sugar. With processor running, pour in melted butter. Pulse until mixture resembles wet sand.
Dump mixture onto prepared pan and press mixture firmly to form a flat ‘crust’. Bake at 350°F for 6 minutes. Remove from oven and crumble into pieces with a fork. Return to oven and bake 2 more minutes. Cool completely. Can be made ahead and stored in an air-tight zip top bag until needed.
Lime Swiss Meringue Buttercream
Makes about 5 cups, or enough to frost a 9-inch layer cake
If you end up making this a 4-layer cake, you may want to make an extra bit of frosting. As is, it was enough for me to frost a 2-layer cake.
6 large fresh egg whites
1 1/4 cup granulated sugar
2 1/2 sticks unsalted butter, room temperature, cut into 1-Tablespoon cubes
1 teaspoons pure vanilla extract
1 tablespoon key lime juice
Pinch of salt
Fill medium saucepan with about an inch of water and bring to a simmer. Add egg whites and sugar to the metal bowl of a stand mixer. Set bowl over simmering water and whisk constantly until sugar has dissolved and mixture reads 140°F on an instant read thermometer.
Attach bowl to stand mixer and using the whisk attachment, beat on medium speed until a glossy white meringue with stiff peaks forms and the bowl no longer feels warm to the touch (about 10-15 minutes). Switch to the paddle attachment. Beating on medium-low speed, add butter one piece at a time, letting each piece incorporate before adding the next. Once all butter is incorporated, scrape down sides of the bowl with a spatula. Continue beating for 10-15 minutes until smooth.
Once smooth, add vanilla, lime juice, salt and zest. Beat until smooth.
(If at any point your buttercream looks curdled or soupy – don’t panic and for pete’s sake don’t throw it out! If it looks curdled, just keep beating. It will come together, I promise. If you’ve been beating it for 15 minutes and it’s still soupy, pop the whole bowl in the fridge for 10 minutes, then continue beating. Repeat as much as necessary until you get a smooth buttercream.)