Preheat: Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.

Boil Pasta: Bring a large pot of salted water to a boil. Cook the tortellini according to package directions (usually 3–5 minutes). Drain and set aside.

Make Sauce: (Skip this step if making a meatless version). In a large skillet over medium heat, cook the ground beef or sausage (with onions and garlic if using) until browned. Drain excess fat. Stir in the marinara sauce, tomato sauce, Italian seasoning, salt, and pepper. Simmer for 5 minutes.

Assemble: Spread a thin layer of sauce in the bottom of the baking dish. Add half of the cooked tortellini. Spoon over half of the sauce. Drop small dollops of ricotta evenly over the top. Sprinkle with half of the mozzarella and cheddar. Repeat the layers. Finish with an even layer of Parmesan cheese on top.

Bake: Cover the dish loosely with foil and bake for 20 minutes. Remove the foil and bake for an additional 10–15 minutes until bubbly and golden brown.

Serve: Let the casserole rest for 5–10 minutes before serving. Garnish with fresh herbs if desired.