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