Preheat oven to 350 degrees and line a cupcake pan with 12 liners. Then set aside.
In a small bowl sift together 1 ¼ cup of cake flour, ¾ teaspoon of baking powder, ⅛ teaspoon of baking soda and ¼ teaspoon of salt. Then set aside.
Add 5 tablespoon of softened butter and ¾ cup of granulated sugar to a large bowl. Cream together with an electric mixer until fluffy, 1-2 minutes.
Then add in 2 egg whites and 1 ½ teaspoon of vanilla. Mix until smooth and pale in color, 1-2 minutes.
Alternate adding ½ cup of buttermilk and the dry ingredients to the butter/sugar/egg mixture. Mix until everything is incorporated. Scrape the sides of the bowl as necessary.
Fill each liner with batter. Each should be about ¾ of the way full.
Bake the cupcakes at 350 degrees for 16-18 minutes, or until a toothpick comes out clean from the centers.
Let the cupcakes cool in the pan for ten minutes, then transfer them to a cooling rack to cool completely.