Pre-heat oven to 400. Get a 9x13 pan spray bottom and sides with non stick cooking spray use 3/4 of a jar of marinara sauce on the bottom add ravioli and top with mozzarella cheese repeat layers starting with ravioli every other layer add more sauce top it all off with Parmesan cheese cover with foil bake for 30 min uncover foil and bake for another 10 mins wait 10 min before serving