01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with cooking spray or oil.
02 - Brown ground beef in a large skillet over medium-high heat, breaking it up with a spoon, about 5 minutes. Drain excess fat if needed.
03 - Add chopped onion to beef; cook 3 to 4 minutes until softened. Stir in garlic, cumin, chili powder, smoked paprika, salt, and black pepper. Cook until fragrant, about 1 minute.
04 - Stir in 1/2 cup enchilada sauce with the beef mixture and remove from heat.
05 - Spread 1/2 cup enchilada sauce on bottom of prepared dish. Layer 5 tortillas over sauce, tearing as necessary to cover bottom.
06 - Spread half the beef mixture over tortillas. Top with 1 cup cheddar and 1/2 cup Monterey Jack cheese.
07 - Repeat layering with remaining tortillas, beef, 1/2 cup enchilada sauce, and the rest of the cheese.
08 - Pour remaining 1/2 cup enchilada sauce evenly over top layer. Sprinkle with any reserved cheese.
09 - Cover dish with foil and bake for 20 minutes.
10 - Remove foil and bake uncovered for 10 to 15 minutes, until cheese is golden and bubbly.
11 - Allow casserole to rest 5 to 10 minutes before slicing.
12 - Garnish with sour cream, cilantro, diced avocado, and sliced green onions as desired. Serve warm.