The entire "canning" process was invented to preserve food. It's ironic then, that we put preservatives in our canned food. We don't need them anymore. We are of the opinion that canned tomatoes should have tomatoes in them. THAT'S IT. Sure, add some spices if you want. Realistically though, we only want to see tomatoes as the ingredient.
It takes one ingredient to make Canned Tomatoes. tomatoes (+spices)