Preheat your oven to 375°F (190°C).
In a large skillet over medium heat, cook the ground beef until browned, breaking it up with a spatula. Drain excess fat.
Add the minced garlic and Italian seasoning to the beef, cooking for another minute.
Stir in the marinara sauce, salt, and pepper; let simmer for 5 minutes.
In a separate bowl, mix the ricotta cheese, half of the mozzarella, and grated Parmesan until well combined.
Cook the tortellini according to package instructions until al dente, then drain.
In a large baking dish, layer half of the beef mixture, then half of the tortellini, followed by half of the ricotta mixture.
Repeat the layers, finishing with the remaining ricotta mixture on top.
Sprinkle the remaining mozzarella cheese over the top, ensuring an even layer.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 15 minutes until the cheese is bubbly and golden.
Let rest for 10 minutes before serving.