Preheat oven to 350°F. Spray a 9 x 13 inch casserole dish with non-stick spray, set aside.
In a large skillet, over medium heat, add the ground beef and onions. Brown the beef, breaking it up it as it browns. When all the beef is just about browned, Mix in garlic. Stir occasionally to blend in the garlic. The meat will be browned through with no pink in the meat. Drain excess fat from pan and discard.
Season meat mixture with cumin, salt, and black pepper.
Increase the heat to medium-high, mix in the diced tomatoes, black beans, and green chiles. Season with salt and pepper. Bring to a low-boil, reduce to medium heat, simmer another 5 minutes to blend flavors.
Taste the cooked beef mix for seasoning, if needed, adjust seasoning.
In the prepared casserole dish, spread a thin layer of enchilada sauce to cover bottom of pan.
On a cutting board or any flat surface, lay out a tortilla, place ⅕ of the beef mixture down the center of the tortilla. Then place a generous helping of shredded cheese, about 2 Tablespoons on the meat mixture. Roll the tortilla up and place seam side down in the casserole dish.
Repeat this process with remaining 7 tortillas.
Pour the remaining enchilada sauce over the filled tortillas. Sprinkle remaining cheese over the sauce.
Bake for 20 minutes, uncovered. The sauce will be bubbly and the cheese all melted.
Remove from oven. Let rest 5 minutes. Serve with your favorite toppings