Preheat the oven to 325 degrees.

Place the egg whites and cream of tartar in a mixing bowl. Beat until frothy.

Add a ½ cup of Swerve sugar substitute and the extracts to the mixing bowl. Continue to beat on high until soft peaks have formed.

Place the almond flour, coconut flour, remaining ½ cup of Swerve, and xanthan gum in a separate mixing bowl. Fluff with a fork for several minutes to get any large lumps out.

Pour half of the dry mixture into the egg white mixture and fold gently to combine. Add the other half and fold gently again.

Grease only the very bottom of a fluted baking dish.

Pour the batter evenly into the baking dish, then smooth the top of the batter.

Bake for 45 minutes until cooked through.

Remove the cake from the oven and immediately invert onto a baking rack.

Allow the cake to cool and serve with your desired toppings.