1 lg. mild onion, chopped
1/4 c. butter
1 1/2 lb. ripe tomatoes
2 1/2 c. chicken stock
3 tbsp. fresh basil, chopped

Saute the onion in butter until soft. Add tomatoes and continue cooking for another minute. Pour in the chicken stock or broth. Bring to a boil, then simmer for 20 minutes. Puree the mixture in a blender, then add basil. Return to the heat until warmed.