Preheat oven to 350 degrees F.

Prepare a 9 X 13-inch baking dish by spraying it with cooking spray.

In a large skillet, brown the ground beef over medium high heat.

Add the chopped onion, homemade taco seasoning and water, reduce heat and allow to simmer for 5 minutes.

Place the crushed Frito chips into the bottom of the baking dish, spreading evenly.

Evenly distribute the taco seasoned beef over the chips.

Sprinkle the cheese over the beef.

Bake for 10 minutes.

After removing from oven, scatter the tomatoes and spinach over the cheese layer, alternating between each.