Preheat the oven to 400F
Separate egg yolks and egg whites into different bowls.
Cook spinach in a pan with no water or butter. Once the spinach is tender, strain. Additional note: Frozen spinach will work just as well, you just have to thaw it and then strain it.
Heat half & half over a medium heat until warm. Add butter and coconut flour and stir mixture continuously until the sauce thickens up. Don't let the mixture boil.
Pour white sauce into a small mixing bowl and season with black pepper, salt, and cayenne pepper. Add room temperature egg yolks and stir.
Add mozzarella, parmesan and the spinach into the white sauce and stir until uniform. Set aside.
Beat the egg whites in a stand mixer. Start on low speed for 2 minutes, add cream of tartar then increase the speed to high until you see stiff peaks.
Stir egg whites into the base in four portions. Stir gently to prevent deflation.
Line parchment paper at the bottom of a spring form pan. Generously spray the pan with cooking spray. Coat the bottom and the walls of the pan with parmesan cheese.
Transfer the soufflé mixture into the baking pan.
Place the pan in the pre-heated oven at 400F then drop the temperature to 375F. Cook for 30 minutes