Prepare the marinade: Place lime juice, zest, ginger, garlic, and scallion in a small bowl, and whisk to combine. Place steak in a shallow dish; cover with marinade, turning to completely coat. Transfer to refrigerator, and marinate 1 hour.
Remove steak from refrigerator 30 minutes before cooking; let sit at room temperature. Heat a grill or grill pan over medium-high heat. Remove steak from marinade, and season with black pepper. Sear steak until browned on the outside and cooked to desired doneness inside, 5 to 6 minutes on each side for medium-rare. Transfer steak to cutting board; let cool slightly, and thinly slice on the bias.
In a large bowl, combine red bell pepper, carrots, cabbage, papaya, cilantro, mint, and bean sprouts, if using. Drizzle with the vinaigrette, and toss well to combine. Arrange vegetables and steak on four serving plates. Garnish each serving with 1 1/2 teaspoons chopped peanuts.