There are recipes floating around that call for flour and butter. They are dangerous and can lead to botulism. Nothing with butter or flour should be canned.

TOMATO SOUP

Do not thicken with flour or other thickeners before canning. You may do so after opening, if desired.

4 quarts chopped peeled tomatoes
3 1/2 cups onions
2 1/2 cups celery
2 cups chopped sweet red peppers
1 cup sliced carrots
7 bay leaves
1 Tbsp. whole cloves
1 clove garlic
1 cup brown sugar
2 tsp. canning salt

Combine all vegetables and seasonings (except sugar and salt). Cook until soft.

Press through food mill.

Add sugar and salt, cook over medium heat for 15 minutes.

Ladle hot soup into hot pint jars. Leave 1 inch headspace.

Process in pressure canner for 35 minutes at 11 lb. pressure dial gauge, 10 lb. weighted gauge.

Makes about 4 pints