Preheat oven to 400 F (for microwave and Instant Pot cooking instructions, see notes).
Slice the stem off of the spaghetti squash then cut it in half. Remove the seeds with a spoon. Place the squash cut side down on a baking sheet (option to use a sheet of parchment paper for easy cleanup). Bake in preheated oven until the noodles are soft, but not mushy, typically around 35-45 minutes but cook times will vary based on the size of your squash.
Once cool enough to handle, flip the squash and use a fork to scrape the flesh into "noodles".
In a large pan over medium heat, melt the butter. Add the garlic and saute until fragrant. Add the spaghetti squash and toss to coat in the butter, I find this is easiest to do with tongs. Cook to remove any water from the squash, about 3-5 minutes.
Remove from heat, and stir in the salt, pepper, parmesan and parsley. Sprinkle with additional parsley before serving, and enjoy!
Notes
Cooking squash in the microwave - Pierce all over with a fork, keep the squash whole, and microwave for 5 minutes. Flip, repeat, then let it rest for 5 minutes before slicing and half, and removing the seeds.
Cooking squash in the Instant Pot - Slice in half, remove seeds and place squash on a trivet in your IP. Pour 1 cup of water on the bottom. Seal, and pressure cook on high for 7 minutes.