Preheat your oven to 400 degrees F. Slice your spaghetti squash lengthwise from stem to tail and scrape out the seeds. Place on a parchment lined baking pan. Drizzle a half tablespoon of olive oil onto each half of the squash and rub it all over with your fingers. Sprinkle some sea salt into each half. Flip the squash over ,cut side down, on the pan. Bake for 1 hour.
Once out of the oven, let cool until you can handle it. Using a form scrape from the sides down to the center of each half and remove "spaghetti" to a bowl. Your shell should be hollow if you scraped as much of the spaghetti as you could. Set aside to make the Alfredo sauce.
Alfredo Sauce
Bring 1/4 cup of the butter, the cream and garlic to a boil in a large saucepan over medium heat. Reduce the heat to a simmer and stir in the egg yolk until well incorporated.
Stir in the onion powder, salt and pepper. continue to simmer stirring, until the sauce thickens, about 15 minutes.
Remove from the heat and stir in the Parmesan cheese, the remaining tablespoon of butter, and any optional ingredients if desired.
Assembly
Once your sauce is done, toss in the spaghetti squash and stir to combine well. Divide in half and spoon back into the empty squash shells to serve. Top with optional crispy bacon and fresh chopped parsley.
Storage: Keep any left overs in an air tight container in the refrigerator for up to 5 days.