1. Arrange top oven rack 6" from top heat source. Heat broiler.
2. Arrange tortilla chips in single layer in 12" skillet (or other oven-proof dish of equal size). Sprinkle beans, tomatoes, peppers and scallions evenly over chips. Sprinkle cheese evenly over chips and toppings.
3. Broil, occasionally rotating pan for even melting, until cheese is bubbly and toppings are hot, 3-5 minutes. Sprinkle with cilantro, if desired. Serve with Pico de Gallo and guacamole, if desired.