- 3 cups cake flour
- 1-1/2 cups all-purpose flour
- 3/4 teaspoon baking soda
- 2-1/4 teaspoons baking powder
- 1-1/2 teaspoons salt
- 1 cup plus 2 tablespoons (2-1/4 sticks) unsalted butter, room temperature
- 2-1/4 cups granulated sugar
- 5 large whole eggs plus 3 egg yolks, room temperature
- 2 cups buttermilk, room temperature
- 2 teaspoons pure vanilla extract
- 6 different icing colors
Preheat oven to 350 degrees F. Line standard muffin tins with paper liners.
Sift together both flours, baking soda, baking powder and salt.
With an electric mixer on medium-high speed, cream butter and sugar until pale and fluffy. Reduce speed to medium.
Add whole eggs, one at a time, beating until each is incorporated, scraping down sides of bowl as needed.
Add yolks and beat until thoroughly combined. Reduce speed to low.
Add flour mixture in three batches, alternating with two additions of buttermilk and beating until combined after each. Beat in vanilla.
Divide batter evenly into six bowls. Dye each bowl of batter a different color.
Scrape a little bit of each hue into a cookie scoop and when full, deposited the rainbow batter into one of the molds in the cupcake tin, filling each 3/4 full.
Bake, rotating tins halfway through, until cupcakes spring back when lightly touched and a cake tester inserted in centers comes out clean, about 20 minutes.
Transfer tins to wire racks to cool 10 minutes. Turn out cupcakes onto racks and let cool completely.
Frost as desired.