In a heavy bottom skillet, heat oil. Add onions and beef; cook till beef is no longer pink; drain; return beef and onions to skillet
Add tomatoes (with liquid), ground cumin, and chile powder; allow mixture to cook until tomatoes are tender and their liquid has thickened
Add drained black beans;
Prepare rice according to directions (optional)
Add cooked rice to beef mixture; top with shredded cheese; bake 15 minutes @350ºF uncovered, or until cheese melts
Garnish with chopped cilantro, sour cream or avocado (optional)
Notes
After browning the beef and onions, drain off any oil, add beef and onions back to the skillet, then add remaining ingredients.
Drain beans before adding them to the skillet.
To make it in advance, cook the beef, beans, onion and tomatoes; cover and refrigerate
When ready to serve, add shredded cheese, cover with foil and bake 20 minutes on 350ºF; remove the foil and bake an additional 5 - 8 minutes, or until the cheese is thoroughly melted.