Ingredients

• 1 2" piece lemongrass, tough outer layers removed, lightly smashed, very thinly sliced
• 1/4 cup (packed) light brown sugar
• 3 tablespoons fish sauce
• 2 tablespoons Asian sweet chili sauce
• 1 1/2 pounds hanger steak, center membrane removed, cut into 4 pieces
• 1/2 cup unseasoned rice vinegar
• 2 tablespoons Asian sweet chili sauce
• 1 teaspoon finely grated lemon zest
• 1 medium cucumber, thinly sliced
• 1 medium carrot, peeled, julienned
• 1/2 small daikon, peeled, julienned
• 1/2 small red onion, thinly sliced
• Kosher salt, freshly ground pepper
• 1/2 cup chopped fresh cilantro
• 1/4 cup chopped unsalted, dry-roasted peanuts

Instructions

1. Combine lemongrass, brown sugar, fish sauce, and sweet chili sauce in a resealable plastic bag. Add steak; seal, turn to coat, and chill at least 3 hours.
2. DO AHEAD: Steak can be marinated 12 hours ahead. Keep chilled.
3. For cucumber salad and assembly: Whisk vinegar, sweet chili sauce, and lemon zest in a medium bowl. Add cucumber, carrot, daikon, and onion and toss; season with salt and pepper. Cover and chill at least 2 hours. Meanwhile, remove steak from marinade and let sit at room temperature 30 minutes. Prepare grill for medium-high heat. Season steak with salt and pepper and grill, turning occasionally, 8–10 minutes for medium-rare. Let rest 5 minutes before thinly slicing. Drain salad. Serve with steak, topped with cilantro and peanuts. DO AHEAD: Cucumber salad can be made 4 hours ahead. Keep chilled.
4. Whisk vinegar, sweet chili sauce, and lemon zest in a medium bowl. Add cucumber, carrot, daikon, and onion and toss; season with salt and pepper. Cover and chill at least 2 hours.
5. Meanwhile, remove steak from marinade and let sit at room temperature 30 minutes.
6. Prepare grill for medium-high heat. Season steak with salt and pepper and grill, turning occasionally, 8–10 minutes for medium-rare. Let rest 5 minutes before thinly slicing.
7. Drain salad. Serve with steak, topped with cilantro and peanuts.
8. DO AHEAD: Cucumber salad can be made 4 hours ahead. Keep chilled.