01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish.
02 - Heat olive oil in a large skillet over medium heat. Add onion and red bell pepper; cook for 3 to 4 minutes until softened.
03 - Stir in minced garlic and cook for 30 seconds until fragrant.
04 - Add ground beef and cook, breaking it up with a spoon, until browned and fully cooked, about 6 to 7 minutes. Drain excess fat if needed.
05 - Mix in black beans (if using), chili powder, cumin, smoked paprika, oregano, cayenne pepper (optional), salt, and black pepper. Cook for 1 to 2 minutes to develop flavors.
06 - Pour in 1 cup enchilada sauce and simmer for 2 minutes. Remove from heat.
07 - Spread 1/4 cup enchilada sauce evenly on the bottom of the prepared baking dish. Layer 5 tortillas over the sauce, overlapping if necessary.
08 - Spoon half of the beef mixture evenly over the tortillas. Sprinkle with 1 cup cheddar and 1/2 cup Monterey Jack cheese.
09 - Layer remaining tortillas, beef mixture, and cheeses. Pour remaining enchilada sauce evenly over the top.
10 - Cover with foil and bake for 20 minutes. Remove foil and bake for an additional 10 to 15 minutes until cheese is melted and bubbly.
11 - Let rest for 5 to 10 minutes before slicing. Garnish with cilantro, scallions, and sour cream if desired.