Preheat Oven to 400 degrees
Place your butternut squash on the cutting board and trim the ends off. Now cut the bulb end off from the neck of the squash so you have two pieces to work with. Peel the skin from each portion using either a vegetable peeler or sharp knife.
Starting with the neck, cut the squash into 1 inch pieces and transfer to a large bowl.
Cut the bulb in half, scoop out the seeds, and chop it into 1 inch pieces. Add them to the large bowl.
Peel the onion and cut it into quarters. Add it to the large bowl with the squash.
Peel the garlic and add it to the large bowl.
Drizzle the vegetables with about 3 tablespoons of oil. Add salt, pepper, cinnamon, nutmeg, brown sugar and cayenne to the bowl. Mix everything very well to combine.
Transfer vegetables to a lined baking sheet, making sure to spread them out in an even layer. Place the tray in the oven and roast the vegetables for 30-40 minutes. Be sure to stir the vegetables halfway through cooking.
You'll know the squash is done when it's very tender. Check for doneness by taking a piece of squash and try mashing it with a fork. If it mashes easily then it's done!
Remove the squash from the oven and let it cool for 5-10 minutes