1. Preheat the oven to 350ºF. Fit a 12-cup muffin tin with cupcake liners. Whisk together the flour, baking powder, baking soda, and salt.
2. Beat butter and sugar until fluffy. One by one, mix in eggs, the egg yolk, and vanilla. Add the flour mixture alternately with the buttermilk, mixing until smooth. Spoon out the batter.
3. Bake for about 25 minutes. Cool. Top with your favorite frosting.
Serves 12. Per cupcake (no frosting): 250 calories, 30g carbs, 3g protein, 85mg cholesterol, and 13g fat.
Next up: Lemon Cupcakes