Carefully cut the spaghetti squash in half lengthwise and scoop out the seeds.
Drizzle the inside of the squash with olive oil, and season with salt and pepper.
Place the squash cut-side down on a baking sheet lined with parchment paper. Roast in the oven for about 30-40 minutes, or until the flesh is tender and can easily be shredded with a fork.
While the squash is roasting, prepare the Alfredo sauce. In a medium saucepan, over medium heat, melt the heavy cream and bring to a gentle simmer.
Add the minced garlic and cook for 1-2 minutes until fragrant.
Gradually whisk in the grated Parmesan cheese (or nutritional yeast) until melted and smooth.
Stir in the nutmeg and season with salt and pepper to taste. Remove from heat.
Once the spaghetti squash is cooked, use a fork to scrape the insides to create spaghetti-like strands.
In a large mixing bowl, combine the spaghetti squash strands with the creamy Alfredo sauce, tossing gently to coat.
Serve warm, garnished with fresh chopped parsley.
Notes
For a vegan option, substitute heavy cream with a plant-based alternative and Parmesan cheese with nutritional yeast.