Preheat oven to 375 degrees. Oil a 9 x 13 inch baking dish. Set aside. Cook ground beef and onion over medium heat until meat is brown and broken up. Discard drippings. Add cumin, garlic, chili powder, salt, pepper, black beans and water. Simmer 10 minutes uncovered or until most of the liquid has evaporated.
Meanwhile, pour 1/2 cup enchilada sauce into prepared casserole dish. Arrange 1/2 of the tortillas to cover the bottom of the casserole. Pour 1/2 cup more enchilada sauce evenly over the tortillas. Spoon in beef mixture, top with sour cream, and sprinkle half the cheese over the top. Arrange remaining tortillas, overlapping on top of the cheese layer. Spread remaining enchilada sauce over tortillas. Top with remaining cheese. Cover with foil and bake 40 minutes. Remove foil and continue baking 5 more minutes, or until bubbling. Serves 6-8.
This recipe may be prepared in advance prior to the cooking stage.