There are several Tomato Soup Cake recipes in my Mom's church cookbook from back in the 50s. Each with it's own twist. None had chocolate though. The one I liked the most, as a kid was spicy and with raisins.
Googling, I found the recipe's evolution via the Campbell's Soup website, right through to one using a boxed cake mix. Though it is a spice mix, not chocolate.
https://www.campbellsoupcompany.com/...up-spice-cake/