Preheat the oven to 375°F (190°C) and grease a 9x13-inch baking dish with olive oil.

Cook the cheese tortellini according to package instructions, usually boiling them for 3–5 minutes until al dente. Drain and set aside.

In a skillet, heat 1 tablespoon of olive oil over medium heat. Add chopped onion and sauté for 3–4 minutes until translucent. Add minced garlic and stir for another minute.

Add ground beef to the skillet with salt, pepper, and Italian seasoning. Cook for 6–8 minutes until browned, then drain excess fat.

Pour marinara sauce into the skillet, stir to combine, and simmer for 3–5 minutes until heated through.

In a large bowl, mix cooked tortellini with beef and marinara sauce, being careful to keep the tortellini intact.

Transfer the mixture to the greased baking dish. Top with mozzarella and Parmesan cheeses.

Bake uncovered for 20–25 minutes until bubbling and golden.

Let the dish rest for 5 minutes before serving, then sprinkle with fresh parsley.