Preheat your oven to 350 degrees. Spray a 9 by 13 inch baking dish with cooking spray and set aside.
In a large skillet for the enchilada sauce, heat 1 tablespoon oil over medium heat. Add 1 diced onion and 1/2 teaspoon kosher salt. Saute until the onion is translucent, about 5 minutes.
While the onion is cooking, add the ground beef to a separate skillet to make the enchilada filling, breaking it up and seasoning it with salt and pepper. Once broken up, add the second diced onion and cook until the beef is cooked through, about 5 minutes.
Stir chili powder and cumin into the onion for the enchilada sauce and cook for about thirty seconds. Then stir in 1 tablespoon all purpose flour. Slowly whisk in chicken stock. Then stir in the tomato sauce and minced garlic. Bring to a simmer and cook, stirring occasionally for 5 minutes.
Once the beef is cooked through, remove from the heat, drain the fat and stir in the green chiles and black beans.
Transfer the enchilada sauce to a blender and blend to make smooth (optional). Pour 1/2 cup in the bottom of the prepared baking dish. Pour 1/2 cup of enchilada sauce into the beef mixture.
Dip 6 tortillas in the remaining sauce to coat them and line the bottom of the casserole dish with them.
Divide the beef mixture in half, and add half of it to the top the tortillas in the pan. Top with 1 cup of cheese.
Dip the remaining 6 tortillas in the enchilada suce and top with the remaining beef mixture and 1 1/2 cups colby jack cheese.
Bake uncovered for 20 minutes or until the cheese is bubbly.