Preheat oven to 350 ℉ (170 ℃)
Combine ¾ cups Gluten-free Flour, ¾ cups Powdered Sugar1, ¼ cups Corn Starch, 1 tbsp Cinnamon2 and ¼ tsp Salt in a medium bowl.
Add 1 ½ cups Egg Whites to a bowl or stand mixer. Beat on high until they become light and foamy. Add 1 tbsp Vanilla. Continue to whip on high speed.
Slowly add ¾ cups Granulated Sugar to the egg whites. Continue to beat egg whites until they reach stiff peaks.
Slowly fold dry ingredients to the egg whites. Be careful not to deflate the egg whites. This is a gentle folding process.
Pour batter into a round tub pan, ungreased. Spread gently and shake pan to smooth the top.
Bake for 35 to 40 minutes. You can test if the cake is done by touching the top of the cake to see if it springs back or inserting a toothpick to see if it comes out clean.
Turn the cake upside down on a cooling rack. Allow it to cool completely before running a knife along the edges and gently tapping the cake out of the pan.
Serve with dairy-free custard, jam or fresh berries.