Combine onion soup mix, canola oil, lime juice, water, minced garlic, lime peel, cumin, oregano, and pepper in a large resealable plastic bag.

Add flank steak to the bag.

Seal the bag and turn to coat the steak with the marinade.

Refrigerate for at least 4 hours, or preferably overnight.

Remove steak from the marinade and discard the marinade.

Preheat grill to high heat.

Grill steak until desired doneness is reached (145°F for medium-rare, 160°F for medium, 170°F for well-done).

While steak is grilling, saute sliced onion and julienned peppers in canola oil in a skillet for 3-4 minutes, or until crisp-tender.

Remove steak from grill and let rest for a few minutes.

Slice steak into thin strips across the grain.

Place sliced steak onto warmed flour tortillas.

Top with sauteed onions and peppers.

Roll up the tortillas.

Serve immediately with sour cream and lime wedges (optional).