In a large skillet, heat olive oil over medium heat. Add diced onion and sauté 3–4 minutes until soft.

Stir in garlic and cook for 1 more minute.

Add ground beef, breaking it up as it cooks. Brown until no longer pink, 5–7 minutes. Drain excess fat.

Stir in black beans, diced tomatoes with green chilies, and taco seasoning. Simmer for 5 minutes. Season with salt and pepper.

Meanwhile, cook tortellini in salted boiling water according to package directions (3–5 minutes). Drain and set aside.

Preheat oven to 350°F (175°C).

In a large bowl, gently combine cooked tortellini with the beef mixture.

Spread a thin layer of enchilada sauce in a 9×13-inch baking dish. Add tortellini mixture and spread evenly.

Pour remaining enchilada sauce on top and sprinkle with cheddar cheese.

Cover with foil and bake for 20 minutes. Remove foil and bake another 10–15 minutes until cheese is bubbly and golden.

Let rest 5 minutes before serving. Top with sour cream and cilantro if desired.