Mix the marinara and crushed red pepper, then spread about half of the mixture on the bottom of an 11x7 baking dish.
2 cups marinara sauce, ¼ teaspoon crushed red pepper
Cook ravioli according to package instructions until they are just al dente (not mushy).
20 ounces cheese ravioli
Before draining ravioli, stir in fresh spinach until slightly wilted (10-20 seconds).
10 ounces fresh spinach
Drain the ravioli and spinach mixture, then spread about half of it over the marinara in the baking dish.
Sprinkle about half of the cheese over the top.
1 ½ cups shredded mozzarella cheese
Distribute the remaining ravioli/spinach on the cheese, then spread with the remaining sauce.
Bake, covered, about 25 minutes.
Remove the dish from the oven, sprinkle the remaining cheese on top, and bake uncovered for an additional 5 minutes or until the cheese is melted.
Notes
You can use frozen spinach if you don't have fresh on hand. Just thaw and squeeze out the excess moisture. No need to add to the ravioli while cooking, simply distribute over top of the ravioli when adding it to the baking dish. You can adjust the amount of crushed red pepper for more or less kick, or skip it completely!