01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish with cooking spray or a small amount of oil.
02 - Heat a large skillet over medium heat. Add ground beef and cook, breaking up with a wooden spoon, until browned throughout, approximately 5 minutes. Drain excess fat from the skillet.
03 - Add diced onion to the beef and cook for 3 minutes until softened. Stir in minced garlic and cook for 1 minute until fragrant.
04 - Mix in chili powder, cumin, smoked paprika, salt, and black pepper. Add corn kernels and black beans if using. Stir to combine and cook for 2 minutes. Remove from heat.
05 - Spread 1/2 cup enchilada sauce evenly across the bottom of the prepared baking dish. Arrange 4 tortillas over the sauce, overlapping as needed to cover the surface.
06 - Spoon half of the beef mixture evenly over the tortillas. Sprinkle with one-third of the combined cheddar and Monterey Jack cheeses.
07 - Pour 1/2 cup enchilada sauce over the beef layer. Place the remaining 4 tortillas on top. Spread the remaining beef mixture over the tortillas, then add another third of the cheese mixture.
08 - Pour the remaining enchilada sauce over the entire casserole. Top with the remaining shredded cheese, ensuring even coverage.
09 - Cover the baking dish tightly with aluminum foil. Bake for 25 minutes to allow flavors to meld.
10 - Remove foil and bake for an additional 10 minutes until cheese is bubbly and lightly golden on top.
11 - Let casserole rest for 10 minutes before slicing to allow layers to set. Serve warm garnished with cilantro, tomatoes, jalapeños, and sour cream as desired.