Preheat oven to 350 degrees.
Line the cupcake tins with paper liners.
Sift flour, baking powder, salt, and baking soda together in a bowl.
Beat butter on high for 30 seconds.
Add sugar and vanilla extract to the butter .... beating until well combined.
Add egg whites, and then eggs one at a time, beating well after each addition.
Alternate adding the flour mixture and buttermilk to the butter mixture, beating on low speed until everything is mixed together.
Add 1/3 C flour mixture to the wet mixture followed by adding 1/3 C of the buttermilk; add 1/3 C flour mixture again then add 1/3 C buttermilk mix on low speed, add 1/3 C of flour and add the rest of 1/3 C of buttermilk mix in low speed until thoroughly blended.
Bake at 350 degrees for 2025 minutes or until an inserted cupcake comes out clean.
Allow to cool in the cupcake tin for 10 minutes.
Remove the cupcakes from the cupcake tin and completely cool on a wire rack.