13/4 cups butter, room temperature
31/4 cups sifted flour
11/2 tablespoons baking powder
1/4 teaspoon salt
1 cup plus 2 tablespoons milk
1 tablespoons vanilla essence
1 3/4 cups granulated sugar
5 egg whites, room temperature
1. Preheat the oven to 350 degrees.
2. Grease cupcake pan or line with cupcake liners.
3. Whisk together the flour,baking powder and salt in a bowl; set aside.
4. Stir the milk and vanilla essence to combine; set aside.
5. Beat butter in a bowl until pale and fluffy, about 3 minutes.
6. Add the sugar: mix until pale and fluffy.
7. With he mixture on low add the flour, alternating with the milk mixture, beginning and ending with the flour. Mix until just combined.
8. In a clean bowl beat the egg whites until soft peaks form. Fold the egg whites in two additions into the flour batter.
9. Divide the batter evenly among bowls and dye each bowl of batter a rainbow color.
10. Evenly distribute the blue batter among the cups, then the yellow, and so on.
Bake for 15-20 minutes.
11. Cool and ice with colored buttercream icing.