Line baking sheet with aluminum foil. Cut squash in half, scrape out seeds, and season with salt and pepper. Drizzle olive oil on aluminum to coat and place squash, cut side down, on foil.
Place in center of oven and roast squash in oven until very soft, one hour or more. Allow to cool slightly and gently peel off skin.
Meanwhile, in large pot, sautee onions, carrots, and celery in small amount of canola oil until soft. Add spices and cook for about two minutes. Add squash pulp and just top with water. Bring to simmer for about half an hour. Add all remaining ingredients and simmer for another half hour. Blend soup and strain through large strainer. Check seasoning and add salt (pepper) as needed. If soup is too thick, add water. If it is too thin, simmer and reduce until thick. Cool.
This recipe is by Boulder-based chef Hosea Rosenberg.