beef flank or round steaks
Each flank steak should weigh between 1 and 1 1/2 pounds.
Place beef steaks in shallow glass or plastic dish.
Mix remaining ingredients and pour over the beef.
Cover and refrigerate at least 8 hours, turning occasionally.
Set oven control to broil.
Place beef on rack in broiler pan.
Broil with the tops about 3 inches from the heat until brown, about 5 minutes.
Turn beef and broil about 5 minutes longer.
Cut beef in thin strips across the grain of the meat.
Serve with tortillas and guacamole if desired.