In skillet, cook ground beef and onions until meat is brown and onions are tender. Drain off excess fat. Stir in taco seasoning mix and tomato sauce, simmer for 5 minutes. Place 3 cups tortilla chips in 2 litre baking dish. Top with half grated cheese, the meat mixture, and then the remaining cheese. Top with additional 2 cups tortilla chips. Bake at 180ºC or 15 minutes. Garnish with sour cream and black olives if desired. Even stir in some jalapenos!!!