Ingredients
1 cup unsalted butter, room temperature1/3 cup vegetable oil1-3/4 cups sugar3 large eggs, room temperature3 large egg whites, room temperature1 tablespoon vanilla extract3 cups cake flour2 teaspoons baking powder1 teaspoon salt1 cup buttermilk, room temperature1/4 cup rainbow sprinklesBUTTERCREAM:1-1/2 cups unsalted butter, softened4-1/2 cups confectioners’ sugar, sifted3 tablespoons heavy whipping cream2 teaspoons clear vanilla extractSoft pink paste food coloring
Preparation
Preheat oven to 325°. Grease a 13x9-in. baking dish. In a large bowl, cream butter, oil and sugar until light and fluffy, 5-7 minutes. Add eggs, then egg whites, 1 at a time, beating well after each addition. Beat in vanilla. In another bowl, whisk flour, baking powder and salt; add to creamed mixture alternately with buttermilk, beating well after each addition. Fold in sprinkles.
Transfer to prepared pan. Bake until a toothpick inserted in center comes out clean, 35-40 minutes. Cool completely on a wire rack.
For buttercream, in a large bowl, beat butter until creamy. Gradually beat in confectioners’ sugar until smooth. Add cream, vanilla and food coloring. Beat until light and fluffy, 5-7 minutes. Frost top of cake with frosting, and, if desired, top with additional sprinkles.
