Two-Layer Cake

1/4 cup unsalted butter ( 1/2 stick), at room temperature

1/2 cup granulated sugar

1 egg

1/2 teaspoon pure vanilla extract

1 teaspoon baking powder

1/2 teaspoon salt

1 cup cake flour or bleached flour

1/3 cup whole milk Vanilla buttercream icing

1 cup unsalted butter (2 sticks), at room temperature

2 tablespoons vanilla extract

1/2 cup whole milk

32 ounces confectioners' sugar Colored flower frosting

1 1/2 cups unsalted butter (3 sticks), at room temperature

1 tablespoon pure vanilla extract

1/2 cup plus 1 tablespoon whole milk

48 ounces confectioners' sugar

4 (or more) different shades of food coloring