This coconut key lime cake has zesty key lime layers, a 7 minute marshmallow coconut frosting, and it topped with toasted coconut!
Total Time:55 minutes
For the cake:
1 cup (230 gm) unsalted butter, at room temperature
2–1/4 cups (450 gm) sugar
3 large eggs, at room temperature
1 cup (240 gm) buttermilk, at room temperature
2 tablespoons key lime zest
6 tablespoons key lime juice
3 cups (420 gm) all-purpose flour
1 teaspoon baking soda
1 teaspoon salt
½ teaspoon baking powder
For the frosting (Adapted from Sarah Kieffer):
5 large egg whites, at room temperature
1–2/3 cup sugar
2 tablespoons corn syrup
¼ teaspoon salt
½ teaspoon vanilla extract
½ teaspoon coconut extract
3 cups toasted coconut
To prepare the cake:
Preheat the oven to 350 degrees and grease 3-8” pans, lining the bottom with a round of parchment paper. Set aside.
In a large bowl or the bowl of a stand mixer, cream the butter and sugar on medium speed for 3 minutes. Scrape the sides of the bowl and add the eggs, one at a time, beating for an additional minute afterward. Combine the buttermilk, zest, and juice, and add half of this mixture to the butter mixture. Scrape the sides of the bowl and add the flour, baking soda, salt, and baking powder stirring on low speed. Once almost combined add the remaining milk mixture. Scrape the sides of the bowl and fold in any unincorporated bits into the batter. Divide the batter among the three pans and bake in the oven until a toothpick inserted comes out clean, about 15 minutes. Allow to cool completely.
To prepare the frosting:
Bring an inch of water to a simmer in a medium-sized saucepan on the stove.
Meanwhile, in a large clean bowl or clean bowl of a stand mixer, whisk together the egg whites, sugar, corn syrup, and salt. Put the bowl over the pot of gently simmering water and stir with a spatula until the sugar has melted. You can test this by carefully rubbing the mixture between two fingers. It should feel smooth. Once the mixture reaches about 165 degrees (about 6 minutes on the stove) remove the bowl from the heat and and being whipping the mixture on medium-high speed with a hand mixer or on your stand mixer until stiff peaks have formed, about 8-10 minutes. Add the vanilla and coconut extract and stir in.
To assemble the cake:
Cut the domes off the baked cake layers. Use a bit of frosting to adhere one layer to an 8” cake board or serving plate. Spoon ¾-1 cup of frosting on top of the layer and spread it flat. Repeat this process with the remaining two cake layers and then use the remaining frosting to frost the cake. If desired, you can coat the cake with the toasted coconut flakes, or you can use a torch to carefully toast the meringue frosting. Cake is best served the day it is assembled.