Why is Tomato Soup called "soupe à la tomate" and not "soupe de la tomate" ?
Shouldn't it be "de la" if you want to say "soup of the tomato" ?
Yes, as I've seen it explained, de means it is substantially the thing that is the object of de. Une cuillère de cuivre = a copper spoon.
Using à means that it is flavored with the thing. Tomato soup is made mostly of either broth or milk, with a healthy dose of tomatoes added. Therefore, it takes the à.
Timor mortis conturbat me.
In both cases, the conversationnal implicature entails that tomatoes are the main ingredient of the soup, but I think that you can still add some other (e.g. in both you would put some salt at least, right?). So there might be a little nuance, but I am not very sensitive to it honestly... But thanks for the remark, I had not thought about it!
Well, yes, when you translate it literally. But when you’re learning a language, translating literally into your own language often makes no sense. So in this case, you just have to accept that it means “tomato soup”. French usually doesn’t translate literally into English very well. And rightfully so!