In a bowl, combine olive oil, minced garlic, lime juice, cumin, chili powder, salt, and pepper.
Marinate the steak in the mixture for at least 1 hour, or overnight for best flavor.
Preheat your grill or grill pan over medium-high heat.
Remove the steak from the marinade and let excess drip off.
Grill the steak for about 4-5 minutes on each side, or until desired doneness.
Remove the steak and let it rest for 5 minutes before slicing.
Slice the steak thinly against the grain for maximum tenderness.
Warm the corn tortillas on the grill for about 30 seconds on each side.
Assemble the tacos by placing sliced steak on tortillas.
Top with onions, cilantro, and salsa before serving.