In cup of blender or food processor, puree chilies, tomato sauce, lemon juice, onion, coriander and pepper sauce. Place steak in large plastic bag. Pour tomato sauce puree over steak. Seal bag well and turn so that meat is well coated. Marinate, refridgerated for about 4 hours. Cook on grill over medium to high heat for about 6-8 minutes per side, basting periodically with marinade. Adjust cooking time for more well done meat.
A zesty, but not overly hot marinade for beef.