Be sure to use the ripest tomatoes you can find.
Put tomatoes, onion, olive oil, garlic, salt, oregano, and pepper in a large bowl and toss to mix.
Let stand, tossing occasionally, until very juicy, about 30 minutes.
Meanwhile, put squash in a microwave-safe plate or bowl. Cover and cook on High until strands of squash separate when flesh is scraped with a fork, about 8 to 10 minutes.
Scrape spaghetti squash from peel with a fork to form strands.
Stir basil into tomato mixture. Mound squash on serving plates and top with sauce.
Photo, recipe and nutritional analysis created by Terry Grieco Kenny for DietsInReview.com