Tiny Rainbow Birthday Cake

Name: Rainbow Birthday Cake
Yield: 1
Ingredients: 1/4 tablespoon butter, melted; 1/2 tablespoon sugar; 1 1/2 teaspoon egg; 1/8 teaspoon vanilla; 2 1/2 tablespoon flour; 1 teaspoon milk; 1/8 teaspoon baking soda; 1/8 teaspoon baking powder; 1/4 teaspoon rainbow sprinkles; Vanilla frosting