Ingredients

• 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.

Instructions

1. 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.
2. 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.
3. Transfer steak to a cutting board; let rest at least 5 minutes before slicing.
4. DO AHEAD: Steak can be marinated 1 day ahead. Keep chilled.