Preheat your oven to 350°F (175°C) and prepare a 9x13-inch casserole dish by spraying it with nonstick cooking spray.

In a large skillet over medium heat, add the ground beef and chopped onion, and cook until the beef is browned and the onions are soft, about 5-7 minutes.

Stir in minced garlic and cook for 1 additional minute.

Stir in 1 1/4 cups of enchilada sauce, followed by the black beans and diced green chiles, and cook for another 1-2 minutes.

Pour 2 tablespoons of enchilada sauce onto the bottom of the casserole dish and start layering with a fourth of the tortillas.

Add one-third of the beef mixture and sprinkle a quarter of both cheddar and Monterey Jack cheeses.

Repeat the layering process two more times, finishing with the remaining tortillas, additional enchilada sauce, and the last of the cheese.

Cover the casserole with aluminum foil and bake for 30-35 minutes. Remove the foil and bake for an additional 5 minutes.

Let the casserole rest for 5-10 minutes and then garnish with diced avocado, fresh tomato, cilantro, and minced jalapeño.