Ingredient:

• CAKE:
• 1/2 cup butter, softened
• 1-1/2 cups sugar
• 2 large eggs, room temperature
• 2 large egg whites, room temperature
• 1-1/2 teaspoons vanilla extract
• 2-1/4 cups all-purpose flour
• 1-1/2 teaspoons baking powder
• 1/2 teaspoon baking soda
• 1 teaspoon salt
• 1-1/2 cups 2% milk, room temperature
• 1/2 cup sour cream
• FROSTING:
• 2 cups unsalted butter (4 sticks), softened
• 12 cups confectioners' sugar, divided
• 1/2 cup 2% milk
• 4 teaspoons vanilla extract
• Food coloring