Sift flour, cornstarch, sweetener, and salt into a bowl. Set aside
Using a mixer, whip egg whites with the cream of tartar until medium peaks form. Add the vanilla little by little
Gently, using a spatula, fold in the flour mixture into the egg whites in 3-4 batches. Be careful, do not deflate the egg whites
Place mixture into a UNGREASED angel food pan and bake for 40-45 minutes or until cake is springy to the touch and the top is golden
Remove from the oven and invert pan onto the neck of a wine bottle to cool completely
Run a knife around the rim of the cake pan to remove the sides. Then run your knife between the cake and the bottom part of the mold to release the bottom part
Serve with sour cream, sugar-free whipped topping, and fresh fruit
Enjoy!
Notes
*You can use 1 1/2 cups of Swerve or Splenda. Just keep in mind that some sweeteners are stronger than others, so read on the label their conversion chart to see how much you would need to replace 1 1/2 cups of sugar.