Heat the chili. Using a round baking dish, cover the bottom with a layer of fritos, a layer of tamales, topped with 1/2 cup chopped onion.
Pour 1/2 of the chili on top of all this and add 4 slices of cheese.
Repeat in the same order with the remaining ingredients, beginning with the chopped onions.
Bake @ 350 degrees until casserole is hot and cheese is melted.