Squash and Sun Dried Tomato Soup

1 butternut squash, cut in half, seeds removed
2 onions, chopped
3 tablespoons butter or oil
1 cup sun dried tomatoes packed in oil, or 1/2 cup dehydrated tomatoes
1 quart chicken stock
1/4 teaspoon chili flakes
salt and pepper
sour cream

Roast squash at 350 until soft, about 1+ hour.  Scoop out flesh after it has cooled.  Meanwhile, saute onions until tender.  Add tomatoes, stock, chili flakes, and squash.  Simmer about 30 minutes.  Puree soup.  Season to taste and top each bowl with a dollop of sour cream.