Preheat the oven to 425°F. Spray a 9x13-inch baking dish with nonstick cooking spray. Set aside.

Bring a large pot of salted water to a boil. Once it has reached a boil, add the tortellini. Cook according to package directions until tender, typically 7-9 minutes.

Drain the tortellini in a sieve or colander and return them to the pot. Add the marinara sauce and Parmesan cheese and stir to combine.

Pour the tortellini mixture into the prepared baking dish. Sprinkle the shredded mozzarella cheese evenly over top.

Bake the tortellini on middle rack of oven until cheese is melted and dish gently bubbles at edges, 11-13 minutes.

Check to see that tortellini are done. Remove from oven or add time as needed.

Allow to rest for 10 minutes before serving.