One bag frozen raviolis, any type (cheese, beef, sausage, etc.)
---or you could use the refrigerated raviolis to save a step
4 cups spaghetti sauce
1 small bag of baby spinach
2 cups shredded mozzarella cheese
Prepare the ravioli as instructed on the package. While they're cooking, get out the other ingredients and spray a large casserole dish with non-stick spray.
Drain the ravioli, pour half in the dish. Cover with half the sauce, half the spinach, and half the cheese. Repeat. Cover dish and bake for 35-45 minutes at 350 degrees. Let stand for at least 5 minutes.
You can personalize this to your family's tastes: add mushrooms, shredded carrots, meatballs, sausage, etc.