Anonymous Modernist 15936

MCAH mentions the addition of baking soda as being the secret to Heinz tomato soup but then after the tease, doesn't give us a recipe for tomato soup I'm going to have a go but I am wondering if I need to amp up the baking soda, compared with carrots, say, due to the fact that the tomatoes are much more acidic and it's the alkaline effect that helps the caramelisation. Has anyone tried and if so, how much did they use and what happened? Thanks!