Preheat oven to 375°F. Cook beef and onion in a large skillet over medium-high heat, breaking up meat, until browned, 6 to 8 minutes. Drain excess fat.

Stir in garlic, chili powder, cumin, paprika, oregano, and salt; cook 1 minute. Add half the enchilada sauce, the black beans, and green chiles. Stir and remove from heat.

Spread about 2 tablespoons reserved sauce in a 9x13 dish. Layer tortilla halves, then half the beef mixture and 1 cup cheese. Repeat layers, ending with a final tortilla layer. Top with remaining sauce and cheese.

Bake, uncovered, 25 to 30 minutes until bubbly. For a crispy top, broil 2 to 3 minutes, watching closely.

Let rest 5 to 8 minutes, then slice and serve with sour cream and cilantro.