Preheat the oven to 350F.

Cut the butternut squash in half and scoop out the seeds. Discard seeds. Place 2 of the 5 tablespoons of margarine and the onion and broth in a casserole dish. Place the squash halves upside down over the onion mixture, and roast, uncovered, until the squash is soft, about 45 minutes to 1 hour.

Puree the squash-onion mixture in a blender or food processor, then pour the pureed mixture into a saucepan. Add the evaporated skim milk and cinnamon and simmer for 5 minutes. Saute the red onion in the remaining 3 tablespoons margarine in a skillet over medium heat for 5 to 6 minutes. Add the sugar and saute until it turns a brownish color and caramelizes, about 4 to 5 minutes.

Divide soup into six bowls and garnish each with sonic of the caramelized onion.