This dish couldn't be any easier; you already did most of the work with the oven-baked tomato sauce found here. Just put 2 cups of this yummy sauce into the bottom of an oven-safe dish big enough to hold all the sausage.
Cut the sausage into quarters, and lay them on top of the tomato sauce, pressing them down slightly.
Bake in a 425-F oven for about 15-20 minutes. Remove from oven and top with dollops of the ricotta, the mozzarella, and Parmesan cheese. Put it back into the oven for about 5 minutes until hot and bubbly!
Serve with your favorite vegetable, and for the non-keto eaters, spoon a generous portion over cooked pasta.