Carefully cut the spaghetti squash in half, lengthwise. I do this by inserting the tip of a sharp knife and carefully rocking the knife back and forth.
Use a spoon to scrape the insides (wet strings and seeds) from the spaghetti squash (see photo for reference).
Brush cut sides of the spaghetti squash with vegetable oil.
Place spaghetti squash, cut side down, on a baking sheet and bake in the preheated for 35-45 minutes (cook time will vary depending on the size of your squash). You'll know your squash is done when a fork can easily scrape strings from your squash. If it seems raw, toss it back in.
Lower the oven temp to 350 F.
In a small bowl, mix the cheeses and set aside.
In a large saucepan, melt the butter on medium heat.
Add cayenne, nutmeg, pepper and salt. Stir ingredients together to combine.
Add the cream and stir everything together.
Stir 1/2 the shredded gruyere and cheddar, stirring constantly so the cheese combo doesn't burn on the bottom
Stir in the spaghetti squash, and evenly coat.
Pour the keto spaghetti squash into a 9x13" casserole dish and top it with the remaining cheese.
Cook spaghetti squash in the oven for 25 minutes, or until the cheese on the top starts to lightly brown around the edges.
Cool slightly before serving, and enjoy!
Add shredded rotisserie chicken for extra protein!