Step 1

Combine soy sauce, ground chile, cumin, oregano, lime juice, sugar, garlic, cayenne, and 2 tablespoons cilantro leaves in a medium bowl. Whisk until sugar is dissolved. Slowly add oil, whisking constantly. Place flank steak inside a gallon-sized zipper-lock bag with marinade. Press out air, seal bag, and allow meat to marinate, turning occasionally, for at least 1 hour and up to 12.

Step 2

Remove steak from marinade and pat dry with paper towels. Ignite a large chimney full of coals and wait until they're covered in grey ash. Spread evenly over 1/2 of grate, leaving the other half empty. Put the cooking grate in place, cover, and allow grill to preheat for 5 minutes. Scrape cooking grates clean, then place flank steak over hot side of grill. cook until well charred, about 3 minutes. Flip steak and continue to cook until second side is well charred, about 3 minutes longer. Transfer steak to cooler side of grill, cover, and cook until the center of the steak registers 125°F on an intant-read thermometer for medium-rare, or 135° for medium, about 5 minutes longer. Transfer to a cutting board, tent with foil, and allow steak to rest for at least 5 minutes.

Step 3

Slice steak thinly across the grain, then cut each slice into 1/2-inch pieces. Serve immediately with warm tortillas, diced onions, chopped cilantro, lemon wedges, and salsa as desired.