1. Finely chop in a food processor onion, garlic, and peppers. Add remaining marinade ingredients and process to blend. Reserve half of marinade and refrigerate. Spread remaining half of marinade on steak, coating all sides. Pierce steak w/fork for extra marinade penetration. Cover and marinate in refrigerator for 2-12 hours.
2. Remove steak and discard meat marinade. Start grilling steak at high heat for 8-10 minutes until tender. Add reserved marinade to onion mixture and heat through. Slice steak across grain into narrow strips. Toss steak strips with onion mixture in skillet.
3. To serve, fill tortillas with the beef-onion combo. Squirt with lime juice and top with cheese, sour cream, and salsa.