Preheat your oven to 400°F (200°C).

Drizzle the insides with olive oil and season with salt and pepper.

Place the squash halves cut side down on a parchment-lined baking sheet.

Roast in the preheated oven for 40–45 minutes, or until the flesh is fork-tender and easily separates into strands.

Once cool enough to handle, use a fork to scrape the flesh into spaghetti-like strands. Set aside.

Meanwhile, heat olive oil in a large skillet over medium heat. Add the chopped onion and sauté for 2–3 minutes until softened.

Add the garlic, carrot, and celery and cook for another 3–4 minutes, stirring occasionally, until the vegetables begin to soften.

Add the ground beef (or turkey) and cook until browned and no longer pink, breaking it up with a spatula as it cooks.

Stir in the crushed tomatoes, tomato paste, oregano, basil, thyme, and season with salt and pepper to taste.

Bring to a boil, then reduce the heat to low and let the sauce simmer for 20–25 minutes, stirring occasionally to allow the flavors to meld.

To serve, divide the spaghetti squash strands among plates or bowls and spoon the warm bolognese sauce over the top.

Garnish with grated Parmesan cheese and chopped fresh parsley, if desired.