Quick Black Bean Soup

For some reason people think that soup is just for winter.  I like them year round because like this one, they are quick. This is not a heavy soup.  I serve it with tortilla chips and a shredded lettuce salad.  Dinner is ready in less than 30 minutes.  It is somewhat like a taco soup but lighter.  You make it as spicy as you want by how hot the salsa is you put in.
Quick Black Bean Soup
2 Tablespoons butter
1/2 small onion, minced (optional)
2 cups chopped cooked chicken
2 cans black beans, drained and rinsed
2 cups chicken  broth
1 cup salsa (as spicy as you like - store-bought or homemade)
The juice of one lime
Melt butter in a medium saucepan and cook onions until golden.  Add chicken and cook until edges start to turn a golden brown.  Add the drained black beans, the chicken broth and salsa.  Simmer together for 20 minutes.  Add the juice of the lime just before serving and just heat through.  Serve with a side salad and tortilla chips or warmed corn tortillas.