In a small bowl, add the marinade ingredients. Whisk to combine.
Place steak in ziplock bag or airtight container. Pour the marinade into the bag, covering the steak.
Place the ziplock bag in your refrigerator and marinate for 2-3 hours
Fire up grill to medium-high heat, about 375-450°F (190-230°C)
While the grill warms up, remove the steak from the marinade. Pat dry with paper towels to remove excess marinade.
When grill is at medium-high temperature, place the steaks on the grill grates over direct heat. Grill for 5 minutes per side, or until internal temperature hits 130°F (55°C) for medium-rare.
Remove steak from grill and wrap in aluminum foil. Rest for 10 minutes.
Unwrap steak and slice meat against the grain into thin strips
Heat the corn tortillas for just 30 seconds on the grill
Serve the steak into the tortillas and top with red onion, queso fresco, and fresh cilantro