Poke numerous holes in the spaghetti squash with a knife and bake in a 375 oven for an hour.
Take out squash, cut in half lengthwise and after discarding the seeds, scrape out the “spaghetti” with a fork.
Layer sauce, squash, cheese, pepperoni and onions in a large casserole dish until all squash is used.
Bake at 375 for about 40 minutes with foil on top.
Take off foil and broil for about ten minutes, until top layer of cheese is golden and bubbly.
Top with basil and enjoy!