Fill crisp lettuce leaves with sliced flank steak topped with a zesty sauce made from lime juice, brown sugar, and minced pepper. Soba noodle salad complements the meaty lettuce wraps and brings another texture to the plate.
Heat a grill pan over medium-high heat. Coat pan with cooking spray. Sprinkle steak with salt and pepper. Place steak in pan; cook 5 minutes on each side or until desired degree of doneness. Remove from pan; let stand 10 minutes. Cut steak diagonally across the grain into thin slices.
Combine juice, fish sauce, sugar, and jalapeño in a medium bowl, stirring with a whisk. Reserve 4 teaspoons juice mixture in a small serving bowl. Pour remaining juice mixture in a large bowl; add steak, tossing to coat. Place 1 1/2 ounces beef in center of each lettuce leaf; top each with 2 tablespoons onion, 2 tablespoons mint, 1 tablespoon cucumber, and 1 tablespoon cilantro. Sprinkle evenly with peanuts; roll up. Serve with reserved juice mixture.
Soba noodle salad: Cook 6 ounces soba noodles according to package directions, omitting salt and fat; drain well. Combine noodles, 1/3 cup chopped green onions, and 1/3 cup matchstick-cut carrots in a large bowl. Combine 1 1/2 tablespoons rice vinegar, 1 tablespoon sesame oil, 1 tablespoon fish sauce, 1 tablespoon low-sodium soy sauce, 2 teaspoons sambal oelek, and 1 teaspoon brown sugar in a small bowl, stirring well with a whisk. Drizzle vinegar mixture over noodle mixture; toss well.