Preheat oven to 350° and line cupcake tins with cupcake wrappers. Set aside.
Cream sugar and butter in mixer with a paddle attachment at medium speed. Add salt and vanilla. Set mixer speed on low and gradually add egg whites. Scrape sides to ensure well combined.
Add the flour, cornstarch, and baking powder mixture alternating it with milk in two batches each. Start with the dry ingredients. Scrape sides to ensure all ingredients are well combined.
Fill cupcake liners 3/4 of the way to prevent it from spilling as the cake rises. Bake for 25 minutes at 350°, or until a toothpick comes out clean. Cool for 25 minutes. Top with Creamy Chocolate Buttercream Frosting or with White Chocolate Raspberry Cream Cheese Icing.
Enjoy!