Marinate flank steak in a mixture of orange juice concentrate, water, lime juice, olive oil, minced garlic, kosher salt, cumin, chili powder, and black pepper for 45 min–2 hrs max.
Pat steak dry before grilling.
Grill 2–3 min per side over very hot coals.
Rest for 5 min, then slice against the grain.
Serve with chopped white onion, fresh cilantro, lime wedges, and warm tortillas.
