Preheat oven to 375°F.
Carefully halve the squash, lengthwise.
With a spoon, scrape out seeds, and the darker orange "goop"!
Line a rimmed baking sheet with foil and coat the foil with a little olive oil.
Sprinkle each half of squash with a little salt (not too much, the Parmesan is salty).
Place squash cut side down on the prepared baking sheet.
Roast for 35 minutes or until easily pierced with a fork, or when it gives a bit when pressed.
Meanwhile, in a large skillet over medium heat, warm 2 Tablespoons of extra-virgin olive oil.
Add garlic and onion and cook until the onion is translucent, about 4-6 minutes.
Add the tomatoes and cook until softened.
With a fork, separate the strands of the spaghetti squash, and scrape into a large bowl.
Toss the "noodles" with the tomato garlic mixture and mix in half of the Parmesan cheese.
Sprinkle with the basil and season with freshly ground pepper.
Once served, pass more Parmesan.