2. With an electric mixer on medium speed cream together the butter and sugar until fluffy, 3-5 minutes. Add the egg yolks. Beat well.3. In a separate bowl combine the flour, baking powder, baking soda, and salt.
4. Add the dry ingredients to the creamed mixture alternately with grapefruit juice and cranberry juice. Fold in the grapefruit zest and chopped cranberries.
5. With a clean electric mixer beat the egg whites until stiff. Gently fold the whites with a spatula into the batter.
6. Fill the cupcake liners one-half to two-thirds full. Bake for 20-25 minutes or until a toothpick inserted in the center of cupcake comes out clean. Cool cupcakes in the pan.
You will need:
1/4 pound (1 stick) unsalted butter, at room temperature
3/4 granulated sugar
2 large eggs, separated, at room temperature
1 1/2 cup all-purpose flour
1 1/2 teaspoons baking powder
1/4 teaspoon baking soda
1/4 teaspoon salt
1/4 cup pink grapefruit juice
1/4 cup cranberry juice
Zest of 1 small grapefruit
3/4 cup chopped cranberries