- 1 medium jalapeño, thinly sliced
- 2 garlic cloves, finely chopped
- 1/4 cup coarsely chopped cilantro
- 1/4 cup fresh lime juice
- 1/4 cup olive oil
- 1 teaspoon kosher salt
- 1/2 teaspoon freshly ground black pepper
- 3/4 teaspoon ground cumin
- 1 pound skirt steak, cut crosswise into 5–6-inch segments
- 8 (8-inch) corn tortillas
- Homemade or store-bought tomatillo salsa (for serving)
- 1/2 medium avocado, sliced
- 1/3 cup sour cream, thinned with a tablespoon of water or lime juice
- Crumbled queso fresco (optional), cilantro leaves, thinly sliced red onion, and lime wedges (for serving)
- Combine jalapeño, garlic, cilantro, lime juice, oil, salt, pepper, and cumin in a large resealable bag or bowl. Add steak and toss to coat; if using bowl, wrap with plastic. Marinate at least 30 minutes at room temperature or chill up to overnight in refrigerator, tossing occasionally.
- Let steak sit at room temperature 30 minutes before cooking if chilled. Prepare a grill or grill pan for medium-high heat. Remove steak from marinade, scraping off any bits that cling to meat; discard marinade. Grill steak 2–3 minutes per side for medium rare. Let rest 10 minutes before thinly slicing against the grain.
- Warm tortillas in a microwave, oven, or over a gas flame. Divide steak among tortillas, then top with salsa, avocado, sour cream, queso fresco, if using, cilantro, and onion. Serve with lime wedges alongside.
- Steak can be marinated 1 day ahead; keep chilled.