- 3 Thai or serrano chiles, with seeds, thinly sliced into rounds
- 1/4 cup tamarind concentrate
- 3 tablespoons light brown sugar
- 1 tablespoon kosher salt
- 1 tablespoon plus 4 teaspoons vegetable oil
- 1 1/2 pounds skirt steak, cut into 4 pieces
- Ingredient info: Tamarind concentrate, often labeled “concentrate cooking tamarind,” is available at Asian markets.
- Whisk chiles, tamarind, brown sugar, salt, and 1 tablespoon oil in a shallow baking dish until sugar is dissolved. Add steak and turn to coat. Cover and chill at least 4 hours.
- Heat 2 teaspoons oil in a large skillet over high heat. Working in 2 batches and adding remaining 2 teaspoons oil between batches, cook steak until deeply browned, 2–4 minutes per side for medium-rare.
- Transfer steak to a cutting board; let rest at least 5 minutes before slicing.
- DO AHEAD: Steak can be marinated 1 day ahead. Keep chilled.