Pumpkin Black Bean Soup

Shannon made this once and I loved it, so she shared the recipe. I've made it several times now. I have also used pureed sweet potato instead of pumpkin, which is also very good. I have simplified it from the original recipe. Quick and easy.

Ingredients
2 15 oz. cans black beans, drained and well rinsed
1 15 oz. can petite diced tomatoes
1 15 oz. can pumpkin (or pureed sweet potatoes)
1 32 oz. box of vegetable stock
3 TB rice vinegar (can substitute sherry vinegar or cider vinegar)
1/2 large yellow onion, diced
approx 3 TB minced garlic
1 TB butter
salt and pepper

Directions
1)Melt butter in the bottom of a large soup pot over medium heat. Season the onions and garlic with salt and pepper and saute them in the butter until the onions are carmelized, about 15 minutes.

2)Add all the remaining ingredients-- vegetable stock, beans, tomatoes, vinegar, and pumpkin. Stir all ingredients together and reduce heat to medium low.

3)Cook the soup for about 25 minutes, stirring occasionally, until it thickens. Remove from heat and serve.