Preheat broiler. Brush salmon with some olive oil, sprinkle with salt and pepper, then broil on both sides, about 6 minutes per side. Cool to room temperature and remove skin. Break salmon into chunks and add to bowl with rice, beans, and scallions. While salmon is cooking, prepare red pepper drizzle. Place roasted red peppers, chipotle pepper, 2-3 tablespoons olive oil and zest of half of the lemon, in a blender or food processor. Blend until smooth, adding oil one teaspoon at a time if necessary. Mix together the remaining olive oil, lemon juice, lemon zest, cumin, and garlic powder. Pour over salmon and rice mixture, then mix gently. Let stand at room temperature for 15 minutes or refrigerate for longer time. Serve on lettuce leaves and drizzle with red pepper puree.