Place steak and salsa in plastic Ziploc bag and allow to marinate in refrigerator for up to 24 hours.
Approximately 30 minutes before cooking, remove steak from marinade and pat dry with paper towels.
Heat grill and place grill pain on grill to heat for the vegetables.
In a medium size bowl, toss onion and bell peppers in oil and vinegar and season to taste with salt and pepper.
Add dry rub to steak. Shake off excess.
Grill flank steak 3-4 minutes per side for medium rare.
Meanwhile, pour vegetables in grill pan and cook for approximately 10 minutes, turning every four or so minutes to get a good char.
After removing the steak from the grill, let rest for at least 5 minutes. Then slice against the grain
Stuff tortillas with steak, vegetables and desired toppings, including any combination of the following: sour cream, cheese, guacamole, salsa.