Beef Enchilada Casserole

 Preheat oven to 350 degrees. Spray a 9 x 13-inch casserole dish with nonstick cooking spray. Brown ground beef in a large skillet over medium heat. When the beef is about halfway browned, add the onion. Continue cooking until the beef is fully browned and the onion is soft. Reduce heat to low, add garlic and cook for 1 minute, stirring continuously. 
 Drain any excess grease. Add 1 1/4 cups enchilada sauce, black beans, and green chiles; cook for 1-2 minutes while stirring to combine. 
 Spread 2 tablespoons of enchilada sauce on 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 the dish with foil and bake for 30-35 minutes or until the cheese is melted and the casserole is heated through. Cook uncovered for 5 minutes. Toss avocado with lemon juice and top the casserole with avocado, tomato, cilantro, and jalapeno. 

Notes :

 Both flour and corn tortillas work for this recipe, choose based on your preference. 
 A Mexican cheese blend can be substituted for the cheddar and Monterey Jack cheese. 
 Add black olives, sour cream, green onions, or salsa for extra flavor and texture.