Marinate the flank steak in olive oil, lime juice, chili powder, cumin, salt, and pepper for at least 30 minutes.
Preheat your grill or skillet over medium-high heat.
Slice the bell pepper and onion into thin strips.
Grill the marinated steak for about 6-7 minutes on each side for medium-rare.
Remove the steak from the grill and let it rest for a few minutes.
In the same skillet, add the sliced peppers and onions, cooking until tender.
Slice the steak against the grain into thin strips.
Warm the tortillas on the grill or in a dry skillet for about 30 seconds on each side.
Assemble the fajitas by placing steak strips, sautéed peppers, and onions on each tortilla.
Garnish with fresh cilantro and serve with lime wedges.