Preheat oven to 350°F and line 2 cupcake pans with paper liners or with nonstick spray.
In a large bowl, sift together cake flour, baking powder, and salt. Set aside.
In a medium bowl, whisk together buttermilk and egg whites. Set aside.
In a large mixer bowl, combine sugar and butter. Beat for 3 minutes, until well combined and fluffy. Add the vanilla extract and mix until combined.
Alternate adding 1/3 of flour mixture and 1/2 of buttermilk mixture to the mixing bowl, beating until just incorporated in between, be sure to begin and end with the flour mixture. Beat for 1 more minute.
Add sprinkles and stir until just combined.
Fill cupcake liners 3/4 full. Bake for 18-20 minutes, until a toothpick inserted in the middle comes out clean. Transfer to a cooling rack and cool for at least 30 minutes before frosting.