Spread a layer of tortilla chips or rounds onto an oven-proof platter or baking pan. In a separate bowl, mix cheese sauce, chiles, and chicken together, and spoon mixture evenly onto chips. Bake at 350 degrees for 8-10 minutes, or until hot. (Watch closely for burning.) Mix tomatoes and salsa together. Spoon mixture onto hot chips and sprinkle with onions (optional). Serve immediately onto heated plates. (This cools very quickly.)