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Confetti Cake with Vanilla-Sour Cream Frosting
A three-layer confetti cake topped with a tangy vanilla and sour cream frosting. It uses a boxed cake mix as a convenient base while upgrading the flavor with a homemade buttercream. The addition of sour cream and salted butter balances the sweetness of the powdered sugar. It makes a cheerful dessert for birthdays or weekend celebrations. The crumb is tender and colorful, paired with a rich, smooth icing.
Ingredients
- 1 (15¼-oz.) pkg. confetti cake mix (plus ingredients listed on box for preparing cake)
- 1½ cups butter, softened
- 4½ cups unsifted powdered sugar
- ½ cup sour cream
- 1 tsp. vanilla extract
- ¼ cup rainbow candy sprinkles, plus more for garnish
Instructions
- 1Heat the oven to 350°F. Make the cake batter following the instructions on the box. Pour the batter evenly into three 6-inch round cake pans that have been greased with baking spray.
- 2Bake the cakes until a wooden pick inserted into the centers comes out clean, taking 20 to 23 minutes. Let the cakes rest in the pans for 10 minutes. Turn them out onto wire racks to cool entirely, which takes about 45 minutes.
- 3Whip the softened butter in a large mixing bowl using an electric mixer on medium speed until it becomes smooth, taking about 2 minutes.
- 4Turn the mixer to low speed and slowly incorporate the powdered sugar, sour cream, and vanilla extract. Whip the mixture until it gets fluffy, pausing sometimes to scrape the sides of the bowl, for about 3 minutes.
- 5Scoop out about 1 cup of the finished frosting into a different bowl and gently mix in the candy sprinkles.
- 6Set a cake plate on a stand or a lazy Susan. Position one cake layer on the plate and cover the top with 1 cup of the plain frosting, leveling it with a bench scraper or an offset spatula.
- 7Do the same with the other two cake layers and 2 cups of the plain frosting. Coat the sides of the cake with a thin layer of frosting, using about a half cup, to create a crumb coat.
- 8Place the cake in the refrigerator to chill until the frosting becomes firm, taking about 30 minutes.
- 9Coat the sides of the chilled cake with a thicker layer of the reserved sprinkle frosting, making it smooth as you work. Transfer any leftover frosting into a piping bag equipped with a medium round tip.
- 10Squeeze dollops of frosting around the top border of the cake. Finish by scattering extra sprinkles over the center of the cake.