Preheat the oven to 400 degrees. Place the squash on a sturdy cutting board. Cut off the stem and bottom end of the squash. Then carefully cut the squash in half lengthwise. Use a spoon to scrape out all of the seeds and stringy bits.
Place the squash cut side down on the baking sheet and roast for 40-45 minutes until it is fork tender. For less browning, roast the squash cut-side up. Don't worry about the darkened edges on the skin, that's where all the deep flavor develops. It isn't burnt.
Optional: During the last 10 minutes of roasting, flip the squash so the flesh side is up. Brush with melted butter and sprinkle with 1 tablespoon of brown sugar (or honey or maple syrup) and 1/2 teaspoon of cinnamon.