Mix the ricotta cheese, egg, Italian seasoning, and a sprinkle of salt and pepper in a bowl.
Layer half of the cooked spaghetti in a baking dish, followed by the meat sauce, then spoon on the ricotta mixture, and top with the remaining spaghetti.
Sprinkle mozzarella and Parmesan cheese on top.
Bake covered with foil for 25 minutes, then remove foil and bake for an additional 15 minutes.
Cool slightly before serving.
Notes
This casserole pairs well with a green salad and garlic bread. Leftovers can be refrigerated for up to 3 days or frozen for up to 3 months.