Preheat oven to 350 degrees.
Line cupcake pan with paper liners.
Sift flour, baking powder, salt, and baking soda together in a bowl.
Beat butter on high for 30 seconds.
Add sugar, vanilla and strawberry extract to the butter until well combined.
Add egg whites, one at a time, mixing after each.
Add eggs, one at a time, mixing after each.
Add flour mixture to the wet mixture; alternating with the buttermilk on low speed until it is thoroughly blended.
Scoop the batter into the lined cupcake holders till 2/3 filled.
Bake at 350 degrees for 20-25 minutes or until an inserted toothpick comes out clean.
Cool for 10-15 minutes.
Remove to a wire rack until fully cooled.