ground beef or sausage
Boil squash (having the water cover the squash) until soft, ~30min. Once squash is softened, cut in half and pit out the seeds. Your spaghetti should be easily removed with a fork. (it should actually look like spaghetti, but will be a little harder in consistency)
While squash is boiling or cooling, cook your beef. Once cooked add desired amounts of tomato/spaghetti sauce.
Combine squash and sauce mixture and TA DA!