I developed this homemade canned tomato soup recipe specifically for the folks who loved my previous tomato soup recipe but wanted one that could be canned.
Remove tomatoes from the heat and let them cool slightly. Working in batches, transfer the warm tomatoes to a food processor, blender, or food mill to puree. If desired, press the tomato puree through a fine-mesh sieve to remove any seeds and skins.
Pour the smooth tomato puree back into the large soup pot. (Using a very wide-bottomed pot will give you more surface area as you reduce tomatoes, making the process take less time.)
The amount of soup you end up with will depend on the type of tomatoes used and how much you reduce the soup. The type of tomatoes used (how much water they contain) will also determine how long the soup needs to cook to reduce down to your preferred consistency.
Reheat your canned tomato soup with some milk or cream, as desired.