@gloriajean
I make a super easy cream of tomato soup using canned tomato sauce.
I use the 8 oz can for 1 serving. Dilute sauce with an equal amount of milk. I usually have 1% or 2% around. Soup will be thin so add 1 tsp. flour to cold soup before heating and it will have more substance. It is more appetizing this way.
Add a bit of sugar to make it more like Campbell's if you wish. Start with 1/4 tsp. and add more if necessary. I use between 1/4 and 1/2 teaspoon.
It's good in a pinch. You might need to add a dash of salt if your is too bland as you said it was salt-free. Good luck.