Preheat oven to 350 degrees and spray a 9 x 13 baking dish with non-stick cooking spray. Set aside.
In a large skillet place ground beef and onion. Break up and brown ground beef until no longer pink and onion is softened. Drain any excess grease.
Stir in taco seasoning.
Mix in enchilada sauce and rotel tomatoes, diced tomatoes or salsa. Turn off burner.
Place 1/2 the (18oz) bag of tortilla chips evenly into prepared baking dish.
Pour 1/2 of the enchilada/ground beef mixture over chips evenly.
Sprinkle with 1/2 of the shredded cheddar cheese.
Place the rest of the tortilla chips over the cheese layer.
Pour the rest of enchilada/ground beef mixture over chips
Sprinkle rest of shredded cheese over meat mixture.
Cover baking dish with foil. (Spray non-stick cooking spray onto foil and place sprayed side of foil over the cheese; this will prevent the foil from pulling the cheese off once removed after it's cooked.)
Bake in preheated oven for 20 minutes. Remove foil from baking dish and bake an additional 20 minutes until bubbly.
Garnish with green onions or cilantro.