Ingredients

1 tablespoon vegetable oil, plus more for grill 

2 tablespoons chile powder, such as ancho, pasilla, or chipotle 

2 tablespoons light-brown sugar 

2 tablespoons soy sauce 

2 tablespoons fresh lime juice, plus wedges for serving 

1 1/2 pounds flank steak 

Coarse salt and ground pepper 

1 large red onion, cut into  1/4-inch rounds 

12 corn tortillas, warmed or lightly toasted 

Easy Tomatillo Salsa, for serving

Preparation

In a small bowl, whisk together oil, chile powder, brown sugar, soy sauce, and lime juice. Place steak in a 9-by-13-inch baking dish and cover with marinade. Turn once to coat steak, then cover dish tightly in plastic wrap and refrigerate 1 hour.

Heat a grill or grill pan to medium-high. Clean and lightly oil hot grill. Remove steak from marinade, letting excess drip off; reserve marinade. Season steak with salt and pepper. Grill onion and steak, flipping occasionally, until onion is lightly charred and steak is medium-rare, about 10 minutes. Brush onion and steak with reserved marinade and cook 1 minute more, flipping once. Place onion on a serving plate. Transfer steak to a cutting board, loosely tent with foil, and let rest 10 minutes before thinly slicing against the grain. Serve steak and onion with tortillas, salsa, and lime wedges.