In a large skillet over medium high heat brown beef and chopped onion. Drain off any grease.
Stir in enchilada sauce and diced tomatoes. Heat through until bubbly. About 2 minutes.
Lightly spray a 9×13 pan with cooking spray.
Spoon a cup of sauce into the pan and spread until even.
Take 1-2 handfuls of chips and slightly crush into a single layer over the sauce.
Sprinkle 1/2 cup of beans over the chips and then top with a third of the cheese.
Repeat for two more layers ending with cheese.
Top with sliced olives and bake for 30-35 minutes until cheese is melted and sides are bubbling. If the cheese is getting to brown on the top cover with foil and continue baking.