Heat olive oil in a large skillet over medium heat. Add diced onion and kosher salt, stirring until the onion is translucent, about 5 minutes.

Add spices by sprinkling in chili powder and cumin. Stir them in and cook for about 30 seconds until fragrant.

Whisk in flour, then slowly pour in the chicken stock while whisking to avoid lumps. Stir in the tomato sauce and minced garlic, letting it simmer for about 5 minutes until slightly thickened.

Brown the beef in a separate skillet over medium heat, seasoning with salt and black pepper until fully browned. Add a second diced onion until tender, approximately 5 minutes.

Combine ingredients by stirring in the black beans and green chiles into the beef mixture.

Prepare the baking dish by pouring a layer of the enchilada sauce into a greased 9x13 baking dish.

Layer tortillas by dipping corn tortillas in the sauce, then layering them into the dish. Add half of the beef mixture and a generous layer of cheese. Repeat the layering process, finishing with a layer of sauce and the remaining cheese on top.

Bake uncovered in a preheated oven at 350°F for approximately 20 minutes until the cheese is bubbly and golden.

Allow the casserole to rest for about 5-10 minutes before slicing.