To prepare marinade, combine first 10 ingredients in a large bowl; set aside.

To prepare fajitas, trim fat from steak. Score a diamond pattern on both sides of the steak. Combine 1 1/2 cups marinade and steak in a large zip-top plastic bag. Seal and marinate in refrigerator 4 hours or overnight, turning occasionally.

Combine remaining marinade, bell peppers, and onion in a zip-top plastic bag. Seal and marinate in refrigerator for 4 hours or overnight, turning occasionally.

Prepare grill or skillet on stove.

Remove steak from bag; discard marinade. Remove vegetables from bag; reserve marinade.

Place reserved marinade in a small saucepan; set aside. Place steak and vegetables on grill rack or skillet coated with cooking spray; cook 8 minutes on each side or until desired degree of doneness.

Wrap tortillas tightly in foil; place tortilla packet on grill rack the last 2 minutes of grilling time. Bring reserved marinade to a boil. Cut steak diagonally across the grain into thin slices.

Arrange about 1 ounce steak, bell pepper wedges, and onion wedges in a tortilla; top with 1 tablespoon salsa, about 1 teaspoon sour cream, and 1/2 tablespoon cilantro. Fold sides of tortilla over filling.

Garnish with cilantro sprigs, if desired.

Serve immediately.