1. Prepare marinade by combining first five ingredients.
2. Trim fat from steak and score a diamond pattern on both sides of steak.
3. Add steak to large sealable plastic bag, add half the marinade and refrigerate for 4 hours or overnight.
4. Cut peppers into thin strips, and cut onion into wedges.
5. In a second bag, add peppers and onions and remaining marinade and refrigerate for the same amount of time.
6. Heat grill or broiler and remove steak from bag, discard marinade.
7. Remove vegetables from bag, reserve marinade.
8. Place reserved marinade in small saucepan and set aside.
9. Cook steak and vegetables on grill or under broiler.
10. Cook 6 to 7 minutes per side or to desired degree of doneness.
11. Wrap tortillas in foil and place on grill for 2 minutes or heat in oven for 5 minutes.
12. Heat marinade to a boil.
13. Cut steak across the grain into thin slices and place on platter with vegetables, drizzle with reserved marinade.
14. Arrange steak, pepper slices and onion wedges evenly on flour tortillas.
15. Top with salsa and sour cream, if desired.