Two layers are good, but three layers are even better, right? This is the ultimate birthday cake—vanilla cake with a classic buttercream frosting—but I’m not the best cake decorator, so I love to simply cover the cake in rainbow sprinkles, which are so festive and beautiful (and anyone can decorate a cake this way with great results). The three layers make it very tall, and it will surely be the centerpiece of any celebration.
Makes 12 servings
1 Preheat the oven to 350°F (180°C). Grease three 6-inch cake pans and line them with parchment paper. (Alternatively, you could use two 8-inch cake pans.)
2 In a large measuring cup, whisk together the egg, egg whites, buttermilk, and vanilla. Set aside.
3 Using a stand mixer fitted with the paddle attachment or a handheld electric mixer, combine the flour, sugar, baking powder, and salt and beat on low speed for 1 minute. (You could also do this by hand using a wooden spoon.)
4 Add the butter and continue to mix on low speed until the mixture resembles coarse bread crumbs.
5 Add the wet ingredients to the dry ingredients in two batches, making sure to scrape the sides and bottom of the bowl in between. Mix until the batter is light, fluffy, and well incorporated.
6 Divide the batter evenly among the prepared pans.
7 Bake for 40 to 45 minutes, until a toothpick inserted into the center of the cake comes out clean. Let the cakes cool in the pans on wire racks for 20 minutes, then turn them out onto the racks to cool completely. (If you are not assembling the cake right away, wrap the cooled layers tightly in plastic wrap and store at room temperature for up to 2 days.)
8 To assemble the cake, place one cake layer on a flat serving plate or cake pedestal. Spread frosting all over the top with a small offset spatula. Top with the second cake layer and repeat with more frosting.
9 Top with the third cake layer. Add a generous dollop of frosting on top and spread evenly, working your way over the top and down the sides until you have a thin layer of frosting over the entire cake. This is called the “crumb layer” and will prevent crumbs from ending up in the final frosting.
10 Refrigerate the cake for at least 30 minutes to set the crumb coat.
11 Take the cake out of the fridge and apply a final layer of frosting all over the cake (see Note below).
12 To apply the sprinkles: Place the cake on a large baking sheet before decorating to catch your excess sprinkles. Pour the sprinkles over the top of the cake, then use your hand to press them into the sides of the cake. Just keep on applying them until they stick all over.
13 Store in an airtight container at room temperature for up to 3 days.
Notes
If your cakes have some knobbly bits, don’t worry—just trim the layers with a serrated knife so all your layers are even.
If you’d like, you can reserve a little frosting in a piping bag fitted with a large star tip, then pipe some rosettes on top of the cake after applying the sprinkles.