In a bowl, combine olive oil, minced garlic, lime juice, cumin, chili powder, salt, and pepper.
Marinate the flank steak in the mixture for at least 1 hour or overnight.
Preheat your grill or skillet over medium-high heat.
Remove the steak from the marinade and shake off excess.
Grill the steak for about 4-5 minutes on each side until desired doneness.
Let the steak rest for 5 minutes after grilling.
Slice the steak thinly against the grain.
Warm the corn tortillas on the grill for about 30 seconds on each side.
Assemble the tacos by placing a portion of sliced steak on each tortilla.
Top with chopped cilantro, diced onions, and salsa.