Simmer tomatoes, chicken broth, celery, and onion for 30 minutes. Mix cornstarch and melted butter together. Add thickening to soup over medium heat. Add brown sugar, salt and pepper to taste. Ready to enjoy, or freeze, if desired. Options for serving include: beaten egg, light cream.
I puree many recipes worth at a time and then freeze in quantities for 1 recipe. Usually I use canned chicken broth or dry bouillon. I also use frozen minced onions and I freeze celery ahead.