Grease three 6-inch round cake pans or two 8 or 9-inch round cake pans with cake release and set aside. (If you don’t want to use cake release, you can grease the pans with shortening and flour them.)
Preheat oven to 325°F.
Add cake mix, all-purpose flour, sugar and salt to the bowl of a stand mixer or a large mixing bowl. (If you don't have a mixer, you can mix by hand with a whisk.)
Whisk dry ingredients together until combined.
Add egg whites, water, vegetable oil, sour cream, vanilla flavor and almond extract to the dry ingredients.
With the paddle attachment, mix on low speed for 30 seconds. Scrape down the sides of the bowl with a rubber/silicone spatula. Continue mixing on low for 2 minutes.
Pour batter evenly into your prepared cake pans.
Bake cakes in preheated oven for 30-35 minutes until a toothpick inserted into the center of the cake comes out with a few crumbs attached. (Start checking the cake after it has been in the oven for 25 minutes.)
Remove cakes from oven and cool on a cooling grid for 10 minutes.
Loosen cakes around the edges with a small spatula and invert onto the cooling grid. (I like to add paper towels because they peel off the cake instead of sticking to the wire grid.) Let cool for 1 hour or more, until cool to the touch.
Once the cakes are cool, frost with your favorite buttercream.
Enjoy!