I decided I didn't have enough tomato soup or ketchup to get through until next fall, so I made a batch of each. Ketchup recipe is here. Tomato soup method is below.
Thrift at Home Canned Tomato Soup
Use 3 parts tomatoes to 1 part onions and 1 part celery. I usually add a few garlic cloves too. I usually do at least a dishpan of tomatoes and end up with 9-12 quarts, but this "recipe" is made to work with what you have, so the individual jars are seasoned after the veggies are cooked.
Once the vegetables are assembled, core tomatoes (no need to peel - big time saver!) and peel onions. Roughly chop veggies. Puree in food processor in batches, making sure to mix onions and celery and tomatoes to get a juicy puree. Pour into stockpot. Add 2-3 bay leaves.
Bring to boil with lid on. Remove bay leaves. Puree again with immersion blender. Ladle into quart jars, leaving at least an inch of headspace because tomatoes really siphon out during canning. Add 1 tsp. salt and a scant tablespoon sugar to each jar. Seal by pressure canning at 10 lbs. pressure for 35 minutes.
To Make Homemade Tomato Soup:
Pour a quart jar of home-canned tomato soup in a saucepan and heat; I do this uncovered to concentrate the soup a bit. Sometimes I add a pinch of dried basil.
Meanwhile, make a white sauce. I do this in my microwave in a big glass measure. Place 3 Tbsp. butter in glass measure and heat for 1 minute. Whisk. Add 3 Tbsp. flour. Whisk. Heat again for 1 minute. Whisk. Add 2 cups milk. Whisk. Heat again for 1 minute. Repeat the heating and whisking until the white sauce is thick.
Once you have a hot, thick white sauce and hot tomato soup base, slowly pour the tomato base into the white sauce, whisking. Do not reverse the order and pour the white sauce into the tomatoes!! Return the soup to the saucepan and heat gently if needed, but do not boil. Taste to adjust salt or add pepper/basil/sugar according to your taste. Serve hot with grilled cheese or crackers.
It's not recommended to waterbath tomato soup because it is a low-acid food due to the added celery and onions.
You can make the white sauce on the stovetop in the classic way, which involves lots of stirring. More on the microwave method in this post. It's a great job for a child.
Microwaves vary. Mine is old and slow, so adjust times accordingly.
Sometimes I add a minced mushroom or two and some minced onion to the butter when I'm starting to make the white sauce. Not usually. I like my tomato soup pretty classically plain. That's also why I only add a pinch of basil, no more.
I discuss the phenomenon of curdled tomato soup and why you must pour the acid (tomato) into the base (white sauce) in this post.