Preheat the Oven to 400°F (200°C). Microwave the spaghetti squash for 4–5 minutes to soften it slightly, making it easier to cut. Let it slightly cool, and carefully cut the squash evenly in half lengthwise. Scoop out the seeds and any stringy bits, then discard.

Drizzle the inside of each squash half with 1–2 teaspoons of olive oil (or lightly mist with oil spray). Sprinkle with salt and black pepper. Place the halves “cut-side down” on a baking sheet and roast for 25–30 minutes, or until the flesh is tender and easily scraped into spaghetti-like strands with a fork. *Tip: Roast time may vary depending on the size of your squash. Start checking at the 25-minute mark by gently scraping one half with a fork. If the strands aren’t soft and tender yet, return it to the oven for 5 more minutes or so until perfectly cooked.

While the squash roasts, caramelize the onions. Heat the remaining 1 Tbsp olive oil in a large skillet over medium heat. Add the thinly sliced onion and a pinch of salt. Cook, stirring every few minutes, for 8–10 minutes or until the onions are deeply browned and caramelized. Be careful not to burn them; lower the heat if necessary.

Remove the squash from the oven and carefully flip the halves over—they’ll be very, very hot, so use a kitchen towel or flexible oven mitt for safety. Use a fork to scrape and fluff the interior, creating spaghetti-like strands.

Assemble and Bake: Divide the caramelized onions and grated Gruyère evenly between the two squash halves, mixing them gently with the squash strands in each spaghetti squash shell. Sprinkle each half with 1 tablespoon of Parmesan cheese. Return the squash to the oven and bake for an additional 10 minutes, until the cheese is melted and bubbly. Garnish with optional minced parsley or thyme and enjoy!