Spread 1/2 cup of the marinara sauce in a 9×13″ baking dish. Top with a handful of cheese, then a layer of ravioli. Place ravioli side by side without any big gaps. Top with a cup of sauce and another handful of cheese. Repeat with another layer of ravioli and sauce, and finish with remaining mozzarella.
Cover with foil and bake for 30 minutes, then uncover and continue baking until cheese is golden and bubbly and internal temp reaches 165ºF, 10-15 minutes more.
Notes
NOTE: No need to boil and drain the ravioli first. It'll cook right in the sauce.