1 red serrano pepper, or red jalapeno pepper, seeded, finely chopped
Combine marinade ingredients. Place beef steak and marinade in food-safe plastic bag; turn steak to coat. Close bag securely and marinate in refrigerator 6 hours or as long as overnight, turning occasionally.
Just before grilling steak, combine salsa ingredients in medium bowl. Cover and refrigerate until ready to serve.
Remove steak from marinade; discard marinade. Place steak on grid over medium, ash-covered coals. Grill, covered, about 8 to 9 minutes for medium rare doneness, turning occasionally. Carve steak into thin slices. Season with salt and pepper, as desired.