Marinate the flank steak with olive oil, cumin, chili powder, garlic powder, salt, and pepper for at least 30 minutes.
Preheat a grill or skillet over medium-high heat.
Cook the marinated steak for about 4-5 minutes on each side for medium-rare.
Remove the steak from heat and let it rest for 5 minutes before slicing.
Slice the bell pepper and onion into strips.
Add the sliced vegetables to the hot skillet and sauté for about 5 minutes until tender.
Slice the rested steak against the grain into thin strips.
Warm the tortillas in a separate skillet or microwave.
Assemble the fajitas by placing steak and veggies on each tortilla.
Garnish with fresh cilantro and lime wedges, then serve immediately.