Mjj21, in this cake, the vinegar is actually used (in conjunction with the soda) as a leavening agent. Have you ever tried mixing vinegar and baking soda by themselves? We did it as kids in school as a science experiment, so I know it bubbles up and overflows like a volcano.

This cake is a pretty classic example of a "depression cake" - they got the name back in the depression when milk, eggs, butter, etc. were really hard to come by and people had to make do without.

I just tried this for the second time: I increased the cocoa to 1/2 cup, used maple extract instead of vanilla, used strong iced vietnamese coffee instead of water, and used balsamic for the vinegar. It is *so* good!