Heat oven to 425 degrees F (220 C). Line a baking sheet with parchment paper for easy cleaning.

Heat the whole acorn squash in the microwave for 1 to 2 minutes, or put it into the heated oven for 5 minutes, so it becomes easy to cut. Slice the squash in half lengthwise. Remove the seeds with a spoon. Then lay the squash skin side up and cut into 1/2-inch (1-cm) slices.

Transfer the squash slices onto the lined baking sheet. Add oil, sugar, and salt. Toss to coat well. Spread into a single layer. Cook until the squash is tender and the surface turns golden about 35 minutes.