Pre-heat oven to 350°F.
Spray a 9 x 13-inch casserole with non-stick spray for ease in cleaning.
In a large skillet, over medium heat, brown ground beef.
When the ground beef is about halfway browned, add the onion.
Cook until the beef is browned and the onion is soft; reduce heat to low.
Add garlic and cook for 1 minute, stirring continuously.
Add 1 1/4 cups enchilada sauce, black beans, and green chilis; cooking for 1-2 minutes while stirring to combine.
Spread 2 tablespoons of enchilada sauce in the bottom of the casserole dish.
Layer 1/4 of the tortillas on the bottom, then spread 1/3 of the beef mixture, and 1/4 of each cheese; repeat these layers two more times.
Top with the last layer of tortillas, the remaining enchilada sauce, and the remaining cheese.
Cover with foil and bake for 30 - 35 minutes or until the cheese is melted and the casserole is heated through.
Remove from oven and cool, covered, for 5 minutes.
Toss avocado with lemon juice.
Top casserole with avocado, tomato, cilantro and jalapeno.