Preheat your oven to 375°F (190°C) and spray a 9x13-inch baking dish with nonstick cooking spray.

In a large skillet, heat olive oil over medium heat, add chopped onions, and sauté until translucent (3-4 minutes). Add minced garlic and stir for another minute.

Add ground beef and cook until browned (5-7 minutes), then stir in marinara sauce and Italian seasoning.

Let the mixture simmer for about 5 minutes until bubbly.

Cook tortellini in boiling salted water according to package instructions (7-9 minutes), then drain.

Fold cooked tortellini into the beef mixture and add optional ingredients if desired.

Transfer the mixture to the baking dish, sprinkle with mozzarella cheese, and bake for 25-30 minutes until cheese is melted and bubbly.

Let cool for a few minutes before serving.