Preheat the oven to 400°F. In a skillet, heat the oil over medium heat until simmering. Add the onions and cook for 5 to 7 minutes or until wilted. Add the beef to the skillet and cook for 7 to 10 minutes breaking the meat up with a wooden spoon until no longer pink, or until an internal temperature of 160°F has been reached. Remove the beef mixture from the skillet to a large bowl and let cool slightly. Add the Hidden Valley® Original Ranch® Sweet Chili Dressing to the beef mixture and stir until well coated. Place one tortilla on a parchment lined or oiled sheet pan. Spoon a fourth of the beef on top of the tortilla. Place another tortilla on top of that, then top with a fourth of the cheese and tomato. Repeat this three more times with the remaining ingredients. Bake the tortilla for 7 to 10 minutes or until the tortilla is crisp and the cheese is bubbly. Serve immediately. Drizzle with more Hidden Valley® Original Ranch® Sweet Chili if desired. Refrigerate any leftovers promptly in a shallow container. Discard any food left out more than 2 hours (or 1 hour if temperatures are above 90°F).