Preheat the oven to 350°. Line a baking pan with foil.
Cut the squash in half, scoop out the seeds, and place in the pan - cut side down.
Add 1/2 cup water and bake for 1 hour.
After an hour, flip the squash right side up, add about 2 Tbsp butter and 2 Tbsp brown sugar to the seed hole of each half and bake for 1 more hour, or until soft. (Add a little more water if it all evaporates.)
Scoop, mash, and serve.
Notes:
Make Ahead: You could easily bake and scoop the squash ahead of time and reheat it in the oven or in a crockpot.