Place top oven rack in the center position and pre-heat oven to 400°F. Line a large, rimmed baking sheet with aluminum foil or a Silpat™ baking sheet. Set aside.
Trim the top and bottom off each spaghetti squash to create a flat surface. Sit the squash upright and slice down the middle with a sharp knife. Scoop out the pulp and seeds with a spoon without piercing all the way through the squash. Reserve seeds and set aside to toast later, if desired.
Brush the edges and inside of each squash half with olive oil. Sprinkle each half with the garlic powder and season with salt and black pepper, to taste.
Place the squash cut side down on the prepared baking sheet and place in the pre-heated oven for 40 minutes, or until the squash is for fork tender.
Remove from oven and cool for several minutes. Once cool enough to handle, flip over the squash and carefully “shred” the inside with a fork to create spaghetti-like strands, leaving the shredded squash inside the squash shells.
Drizzle the melted butter over the spaghetti squash and top each with some Parmesan cheese. Place back into the oven until the cheese is melted and starts to brown.
Remove from oven and serve immediately with some freshly chopped parsley sprinkled on top. Enjoy!