2-1/4 cups self raising flour
1 tablespoon baking powder
1/2 teaspoon salt
1/2 cup butter, softened
1-1/2 cups sugar
4 egg whites
2 teaspoons vanilla
1 cup milk
zest of 6 key limes or 1 large lime
Preheat oven to 180°c
Grease and flour cupcake pans(or use liners). Combine flour, baking powder and salt in medium bowl; set aside. Beat butter and sugar in large bowl with electric mixer at medium speed until light and fluffy. Add egg whites, two at a time, beating well after each addition. Add vanilla; beat until blended. Add lime zest. With electric mixer at low speed, add flour mixture alternately with milk, beating well after each addition. Pour batter evenly into prepared pan.
3.Bake 20-22 minutes(for full size cupcakes) and 15 minutes(for mini) or until wooden toothpick inserted into centers comes out clean. Cool cupcakes in pan on wire rack 10 minutes. Remove from pan and allow to cool completely on rack.
