Seared Steak Lettuce Cups

Ingredients

• 1/4 cup finely chopped English hothouse or Persian cucumber
• 1/4 cup thinly sliced scallions
• 1 1/2 tablespoons fresh lime juice
• 1 teaspoon finely grated peeled ginger
• 1/2 teaspoon kosher salt, plus more
• 1 (8-oz) flank steak
• 1/4 teaspoon chili powder
• 16 small crunchy inner leaves of butter lettuce, romaine, or endive
• 2 tablespoons chopped salted roasted peanuts
• 2 tablespoons thinly sliced fresh mint leaves
• Asian sweet chili sauce is available at Asian markets, many supermarkets, and amazon.com.