In a mixing bowl, combine olive oil, chili powder, cumin, garlic powder, salt, and black pepper. Add the flank steak and coat well. Let marinate for 10 minutes.

Preheat the grill to medium-high heat. Grill the steak for about 5 minutes on each side or until desired doneness.

Remove from the grill and let the steak rest for 5 minutes before slicing.

Warm the corn tortillas on the grill for about 30 seconds on each side.

Slice the grilled steak against the grain into thin strips.

Place a few strips of steak on each tortilla. Top with shredded lettuce, diced tomatoes, sour cream, and chopped cilantro.

Serve with lime wedges on the side.