1 TB vegetable oil plus more for grill 3 TB Maruso Ghost Pepper Soy Sauce (can also use regular Maruso Soy Sauce and 3 TB of your favorite chili spice powder such as Ancho or Chipotle) 2 TB light brown sugar 2 TB fresh lime juice plus wedges for serving 1 ½ pounds flank steak (can substitute flap meat or skirt steak) Coarse salt and ground pepper 1 large red onion, cut into ¼ inch rounds 12 corn tortillas, warmed or lightly toasted Fresh salsa
(1) In a small bowl, whisk together oil, Maruso Ghost Pepper Soy Sauce, brown sugar, and lime juice. Place steak in a 9x13 baking dish and cover with marinade. Turn once to coat steak, then cover dish tightly in plastic wrap and refrigerate 1 hour.
(2) Heat a grill or grill pan to medium-high. Clean and lightly oil hot grill. Remove steak from marinade, letting excess drip off, reserving marinade. Season steak with salt and pepper. Brush onion with some of the reserved marinade.
(3) Grill steak until medium rare (about 10 minutes) and onion until slightly charred. Brush the remaining marinade over the steak and grill an additional minute, flipping once.
(4) Place onion on serving plate. Transfer steak to a cutting board, loosely tent with foil, and let rest 10 minutes before thinly slicing against the grain. Serve with onions and tortillas, salsa and lime wedges.