Preheat your oven to 375°F (190°C) and prepare your baking dish with nonstick spray.

Heat olive oil in a large skillet and sauté chopped onions for 3-4 minutes until translucent, then add minced garlic and ground beef, cooking until browned.

Pour in marinara sauce and Italian seasoning, stirring to combine, and let it simmer for about 5 minutes.

Cook cheese-filled tortellini in boiling salted water according to package directions until al dente, then drain.

Fold the cooked tortellini into the skillet with the meat sauce until well-coated.

Transfer the mixture to the prepared baking dish, sprinkle mozzarella on top, and bake for 25-30 minutes until cheese is bubbly and golden.