Preheat oven to 400°F (205°C).
Cut spaghetti squash in half lengthwise.
Scoop out seeds and stringy pulp.
Place squash cut-side down on a baking sheet lined with parchment.
Bake 35–50 minutes, until tender when pierced with a fork.
Remove from oven and let cool 5–10 minutes.
Use a fork to scrape the flesh into spaghetti-like strands.
Season with salt and pepper, and toss with olive oil or butter if desired.
Serve with your favorite sauce, such as marinara or pesto.