Position a rack in the upper third of the oven and preheat to 500 degrees . Line a baking sheet with parchment. In a medium skillet, melt the butter over medium-low heat until foamy, 2 to 3 minutes. Let the foam subside and cook just until the butter turns golden and gives off a nutty smell, about 1 minute. Remove from heat and stir in the brown sugar, five-spice powder, salt and 1/4 cup water. Cook over medium-low heat until syrupy, about 3 minutes. Keep warm.
Pierce the squash flesh with a fork. Dip each squash slice into the glaze to coat, then place cut side down on the prepared pan and roast for 12 minutes. Remove from the oven, flip the squash slices over and brush with more glaze. Continue roasting until the squash is tender and deep golden, 7 to 10 minutes. Drizzle with the remaining glaze before serving.