This was a challenge! I have never made a gluten free sugar free angel food cake before. It took a long time to prepare because I found the flour mixture was a bit more dense then if I'd used regular flour. But, I am happy with the result none the less.
Preheat oven to 325'F. Position the rack in the lower part of the oven.
Combine flour, xanthan gum together and sift 3 times.
Beat the egg whites on low speed until they begin to get frothy. Add the cream of tartar and salt, increase the speed to medium continue to beat until the egg whites are billowy mounds. Pour the agave nectar about one tablespoon at a time into the egg whites until all the agave is incorporated and the eggs are in the soft peak stage. Do not beat to the stiff stage, it will make folding the flour in difficult.
Pour in the vanilla and lemon juice, mix until just incorporated.
Sift the flour over the egg whites about 3 tablespoons at a time. Fold in very gently making sure you cut down to the bottom of the pan. Do not stir, this will deflate the egg whites, also move very slowly. Use all the flour, make sure it's all folded in well.
Pour the batter into your angel food cake tube pan and cut through the egg mixture with a knife to get the air bubbles out. Smooth the top of the batter with the spatula.
Bake for 50-60 minutes, until golden brown and the cake springs back when touched. Check after 50 minutes, some ovens are hotter then the other.
When the cake is done, remove from the oven and immediately invert on a platter or on a large bottle. Cool for 2-3 hours. To remove cake, place the cake tin on its side and run a thin long flexible metal blade around the outside, pushing against the pan, then use a long, thin boning knife to loosen the part around the middle of the tube. If you have a pan with a release bottom, pop the cake out. Use a thin spatula to release the cake from the bottom.
Serve with whipped cream and strawberries or your favorite fruit. Enjoy!