Heat a splash of olive oil in a large skillet over medium heat. Add diced onions and sauté for about 3-5 minutes until translucent.

Incorporate minced garlic and ground beef into the skillet. Cook for 6-8 minutes, stirring frequently, until browned. Season with taco seasoning, salt, and pepper.

Stir in drained black beans and diced tomatoes with green chilies. Let simmer for about 5 minutes.

Bring water to a boil in a separate pot and cook cheese tortellini according to package instructions, about 3-5 minutes. Drain and fold into beef mixture.

Preheat oven to 350°F (175°C).

In a large baking dish, layer the beef-tortellini mixture, pour enchilada sauce over the top, and sprinkle with shredded cheddar cheese.

Bake for about 20 minutes until cheese is bubbly and golden.

Let cool for a few minutes, serve hot, garnished with sour cream and fresh cilantro if desired.