Preheat your oven to 425°.
Slice your spaghetti squash in half and scoop out the seeds. Place both halves face down in a cake pan with water covering the bottom and bake for 25-30 minutes.
Once cooked, remove from the oven to cool. Once the spaghetti squash is cool, scrape out the “noodles” with a fork. Be sure not to scrape too much of the edges off as you'll want a sturdy boarder to keep it's shape.
In a skillet, heat the marinara sauce, spinach, garlic and onion in avocado oil for a few minutes. Once warm, spoon on top of the “noodles.”
Top with cheese and pepperoni.
Return to the oven for 10 minutes. Once cooked, broil for 2-5 minutes if you'd like to brown the cheese slightly. Be sure to watch it as it can burn quickly!
Once the cheese has slightly browned, remove from the oven and serve with fresh basil and a sprinkle of salt and pepper.