Preheat the oven to 425 degrees. Coat a shallow baking sheet pan with cooking spray.
Cut the squash in half lengthwise and scoop out the seeds. Place cut side up on the sheet pan, and use the point of a small knife to make several 1-inch slashes into the squash, taking care to not cut through to the skin. Drape loosely with foil and bake 1 hour 15 to 1 hour 30 minutes, until very tender when pricked with a fork.
Use a spoon to scoop out the flesh, leaving a ½-inch border all the way around. Mash with a large fork and stir in the butter until it is melted. Add the salt, cinnamon, nutmeg, coriander, dried sage, and pepper and stir well. Place the mixture back into the squash shells and sprinkle with the Gruyere. Return to the oven until the cheese is melted, about 3-5 minutes.
Nutritional analysis for each serving: 188 calories, 6 g protein, 32 g carbohydrates, 6 g fiber, 6 g fat, 4 g saturated fat, 390 mg sodium