Chipotle Skirt Steak Tacos with Smoky Tomatillo Salsa

Preheat grill to medium-high.

Grill tomatillos, turning occasionally, until blackened and very soft, about 10 minutes total. Transfer to a baking sheet and let cool completely, about 15 minutes.

Meanwhile, cook garlic in a small dry skillet over medium heat, turning occasionally, until blackened in spots and soft, about 10 minutes. Transfer to a plate. When cool enough to handle, remove the papery skins.

Scrape the tomatillos and any juices into a mini food processor. Add the garlic, 3 chipotles and 1/4 teaspoon salt. Pulse until coarsely pureed. Transfer to a bowl and set aside.

Puree the remaining chipotles and the adobo sauce in the food processor. Brush steak with the puree and sprinkle with 1/4 teaspoon salt. Brush onion with oil and sprinkle with the remaining 1/4 teaspoon salt.

Oil the grill rack. Grill the onion rounds, turning occasionally, until golden and soft, about 10 minutes. Grill the steak, turning once, until an instant-read thermometer inserted into the thickest part registers 125 degrees F for medium-rare, about 3 minutes per side.

Transfer the steak and onion to a cutting board and let rest for 5 minutes. Coarsely chop the onion and slice the steak against the grain. Serve the steak and onion in tortillas with the reserved salsa and cilantro, if desired.