Preheat the oven to 425 degrees F. Line a baking sheet with parchment paper for easy clean up.
Give the squash a quick rinse.
Cut the blossom end and stem end off of the squash.
Cut the squash into rings that are 2 inches wide.
Use a spoon to scrape out any seeds from the middle of the rings.
Place the rings on the baking sheet, and sprinkle lightly with salt.
If you have time, let the rings rest for 15 minutes (so that the salt will bring some of the water out of the squash -- this helps but isn't crucial.)
Cover the pan tightly with foil, and bake for 10 minutes (the foil helps to steam the squash).
Uncover and bake for an additional 20 to 30 minutes, until the squash is very tender and pulls apart with a fork.
Remove from the oven and shred. Add the shredded squash to a medium bowl, and discard the skin.
Toss the shredded spaghetti squash with the butter, parmesan, and plenty of salt and pepper to taste.
Serve right away.
Notes
Sometimes I'll leave the spaghetti squash inside the little rounds that it baked in and add a little butter, parm, and salt and pepper to each one. It's like making single serve portions, and my kids think that it's fun to eat it out of the skin.
Be sure to use a big, sturdy, SHARP knife to cut through the squash. Sometimes the shell of winter squash, like spaghetti squash, can be a little tricky to get through.
When picking out your spaghetti squash at the store, make sure it's skin is clear and free of cracks, blemishes, and soft spots. A good one will feel a little heavy for it's size, too.