Preheat oven to 425°F. Lightly spray two rimmed baking trays with cooking oil.
Cut squash crosswise into 1-inch (2.5 cm) slices.
Use a round cookie cutter or a small can or jar to remove seeds from the middle of each slice. Place slices on prepared trays.
In a small bowl in the microwave, melt together butter and brown sugar. Using half the butter mixture, brush tops of squash with butter mixture and very lightly sprinkle squash slices with salt and pepper.
Transfer trays to oven and roast 30 minutes or until golden brown and tender, turning once halfway through, and brushing other side with the remaining butter and brown sugar mixture
Transfer squash slices to serving platter and sprinkle with parsley and pomegranate arils.