Preheat oven to 400℉ and grease a 9x13 baking dish.
In a pan, cook the sausage with the onion.
Once cooked, remove the excess grease then add in the sauce's and stir well. Now add and stir in the tortellini.
Add a half layer of the tortellini mixture to the baking dish and top with 1/2 cup mozzarella cheese. add the rest of the tortellini mixture from the pan and top with additional cup of cheese.
Bake covered for about 40 minutes, uncover and bake additional 10 minutes.