Cook and crumble ground beef in a large Dutch oven over medium heat until browned. Pour into colander and rinse with hot water until water runs clean. Take handfuls and rub between hands to crumble into fine pieces. Rinse again.
Melt butter in large Dutch oven over medium heat. Add onions and garlic; sauté until tender, about 5 minutes. Add ground beef, flour, oregano, cayenne pepper, chili powder, cumin, salt and ground black pepper. Stir to mix well. Add Rotel tomatoes and green chilies, and tomato sauce; mix well. Cover and simmer over low heat for 1 hour. Add black beans; cover and simmer an additional 30 minutes.
Serve Chili in bowls topped with chopped onions, crushed tortilla chips and shredded cheddar cheese. (Yield: 4 servings)
*May also use ground chicken or ground turkey.
Variation: Serve warm chili on a bed of shredded lettuce and chopped tomatoes to make a taco salad. Garnish with chopped onions, crushed tortilla chips and shredded cheddar cheese.