Preheat oven to 350°F. Line muffin pan with baking cups.
In large bowl, sift together flour and baking powder.
In large bowl, beat butter and sugar with electric mixer until light and fluffy. Add vanilla; mix well. Add flour mixture alternately with milk; mix well. In separate clean bowl, beat egg whites until stiff but not dry; fold into batter. Fill baking cups 2/3 full.
Bake 17-19 minutes or until toothpick inserted into center of cupcake comes out clean. Cool cupcakes in pan on cooling grid 5 minutes. Remove from pan; cool completely..