Heat oven to 350 degrees. Generously coat a large flute pan with cooking spray on the fluted center and bottom only, but NOT the outer sides.
In stand mixer bowl, combine egg whites, cream of tartar, xanthan gum, guar gum, baking powder, stevia and extracts.
Beat on low for 30 seconds, then increase mixer to high and beat until very stiff peaks form, about 4 minutes. The mixture will be airy, voluminous and thick.
Into a small bowl sift the protein powder, almond flour and powdered egg whites. Sprinkle 1/2 of the dry ingredients over the egg whites. Run the mixer at medium for 5 seconds, just until dry ingredients are incorporated. Sprinkle remaining dry ingredients over the egg whites and mix again just to incorporate.
Increase mixer speed to high for 5 seconds.
Scrape sides of the bowl with silicone spatula and gently fold the mixture once or twice. Transfer 1/2 the mixture to the prepared pan, then use spatula to smooth the top. Repeat with remaining mixture. Firmly tap the pan on the counter to help eliminate air bubbles.
Bake 35 minutes. Remove the pan from the oven and overturn the pan and cool upside down. When cooled, release the cake running a knife along the outside of the pan.