Preheat Oven: Preheat your oven to 350 degrees Fahrenheit.
Cook Beef and Vegetables: In a large skillet, cook the ground beef, red bell pepper, and onion over medium-high heat until the beef is browned and the vegetables are tender.
Season the Mixture: Add the taco seasoning, oregano, and salt (if using), and cook for 1 minute.
Add Salsa and Beans: Mix in the salsa and black beans, then remove the skillet from the heat.
Layer the Casserole: Layer two tortillas in the bottom of a 9x13-inch baking dish. Add ⅓ of the meat mixture and ⅓ of the cheese. Repeat for two more layers, ending with cheese on top.
Bake: Bake at 350 degrees Fahrenheit for 15-20 minutes until heated through and the cheese is melted. Slice and serve.