Whip Egg Whites: Start by adding 12 large egg whites to a clean mixing bowl. Add cream of tartar and a pinch of salt; beat with an electric mixer on high speed until soft peaks form.
Mix in Sweetener: Slowly add powdered erythritol while whipping today holds its peak form.
Fold in the Flour: Sift almond flour over whipped mixture and gently fold it in with a spatula and be sure you do not deflate your batter.
Transfer to Pan: Pour batter into an ungreades angel food cake pan, smooth the surface evenly.
Bake: Preheat oven to 350 degrees and bake for 35 minutes or until golden brown.
Cool and Serve: Flip the pan over to cool for 30 minutes, remove, and then slice. Serve plain or with berries.