Preheat oven to 350º.
Cover cookie sheet with a sheet of foil, spray with nonstick cooking spray.
Cut spaghetti squash in half, length wise. These things are very hard, and HARD to cut; make sure you have a big, sharp, scary knife. Place halves on cookie sheet flesh side down.
Bake for 35 minutes.
Mix cumin in to chili, reheat chili if leftover.
Remove the squash from oven and scoop out seeds with a large spoon. It will be VERY hot so be sure to protect your hands with a pot holder to get a good grip on the squash.
Use a fork to scrape the flesh of the squash into "noodles" and place into bowls.
Scoop out chili with a slotted spoon so you get the thickest parts of the chili and place on top of the squash.
Add chopped onion on top of the chili.
Pile on desired amount of cheese.