1. Preheat the oven to 400°F (200°C).

2. Cut the spaghetti squash in half lengthwise using a sharp chef’s knife.

3. Scoop out the seeds with a spoon or ice cream scoop.

4. Brush the cut sides with olive oil and season with salt and black pepper.

5. Place squash halves cut-side down on a baking sheet and roast for 35–45 minutes until tender.

6. Allow the squash to cool slightly, then use a fork to scrape out strands.

7. Warm the marinara sauce in a saucepan over medium heat.

8. Toss the roasted squash strands with the warmed sauce.

9. Top with grated Parmesan, fresh basil leaves, and red pepper flakes if desired.

10. Serve immediately while warm.