Pre-heat oven to 350 degrees F and place the rack in the middle
Separate eggs, being careful not to get any yolk into the whites. Crack an egg over one small bowl, separate the egg and transfer the egg white to a large mixing bowl. Repeat with remaining eggs.
In a medium sized bowl, sift together 1/4 cup sweetener and 1 cup arrowroot starch.
In the large mixing bowl, use an electric mixer to beat the egg whites on Medium High speed until foamy, 30 seconds. Keep the speed at Medium High for the rest of the recipe.
Add cream of tartar, almond extract and vanilla extract and beat until soft peaks form.
Slowly beat in 1/2 cup sweetener, 1 tablespoon at a time, until soft glossy hills form.
Slowly beat in arrowroot mixture, 1/4 cup at a time, until smooth.
Pour the batter into a 12 inch ungreased tube pan and run a fork through the batter to pop any large air pockets. Smooth the top of the batter with a spatula.
Bake for 35-40 minutes until the cake has doubled in size and the top is a medium brown
Immediately invert the pan. Air needs to be able to circulate around the pan as it cools. If the pan has legs, do nothing, but if not, hold the pan above the counter, using a bottle or can. Cool for 1 1/2 – 2 hours until completely cooled.
Use a knife to carefully cut around the sides of the pan to release the cake. Pull apart the two pieces of the pan. Slice around the top of the pan. Slice around the inner tube of the pan. Carefully release the cake.