How to Make It
Preheat oven to 425℉.
Peel butternut squash down to the bright orange flesh. Cut top and bottom off, then cut down the middle to form two halves. Scoop out the seeds and discard.
Coat sheet pan with cooking spray. Place squash halves face down. Spray squash with cooking spray, and top with ⅛ tsp each of salt and pepper.
Roast squash for 15 minutes.
While squash is roasting, combine Dijon, vinegar, sage, maple syrup, and ¼ tsp each of salt and pepper in a small bowl.
Remove squash from oven, and place halves on a cutting board. Carefully slice the flesh into ¼ inch slices, taking care not to cut through to the bottom. Return to oven. Set a timer for 30 minutes.
Place butter into a skillet and heat gently until it is browned. Whisk butter into mustard and vinegar mixture.
After 30 minutes of roasting, remove squash from oven and drizzle with half of the butter sauce. Return to oven. After final 15 minutes of roasting, remove squash and drizzle with remaining mixture. Sprinkle with sage. Serve warm.