Melt the butter in a (3 Qt.) saucepan over medium heat. Add the bell peppers
and onion. Cook, stirring occasionally, until the onion is soft but not
browned. Mix in the cumin and cayenne. Add the chicken broth. Bring to
a boil. Cover. Reduce heat. Simmer for 20 minutes. Scoop out the vegetables.
Transfer the vegetables to a blender or food processor. Add a little broth.
Process until smooth. Return the puree to the broth in the pan. Mix in
the lemon juice. Adjust seasoning. Reheat to serving temperature. Serve
hot.