-
1
Adjust oven rack to center of oven. Heat to 325 degrees. Line muffin pans with baking cups; set aside. In a medium bowl, sift together flour, baking powder, salt, and baking soda; set aside.
-
2
In the bowl of a heavy-duty electric mixer fitted with the paddle attachment, beat the butter and sugar on medium speed until light and fluffy, 3 to 5 minutes. With mixer running, add eggs and vanilla extract; beat until combined.
-
3
With mixer on low speed, add 1 cup reserved flour mixture; mix until combined. Add 1/2 cup buttermilk; combine. Alternate adding flour mixture and buttermilk, ending with flour, until all has been incorporated.
-
4
Divide batter evenly between baking cups. Bake until light golden brown and a cake tester inserted into middle comes out clean, about 25 to 30 minutes. Rotate pans halfway through baking. Transfer pans to a wire rack to cool.
-
5
Make the frosting: In a heat-proof bowl, combine egg whites, sugar, corn syrup, cream of tartar, and 5 tablespoons cold water. Set bowl over a pot of rapidly boiling water. Using a handheld electric mixer, beat mixture on medium-low speed for 4 minutes. Beat on high speed 3 minutes more or until soft peaks form. Remove from heat; add vanilla. Continue beating until glossy and spreadable, 3 to 5 minutes more. Use frosting immediately. (Makes 3 cups)
-
6
Frost cupcakes with seven-minute frosting. Decorate with raspberries and blueberries.
