Both the "tomato soup" and "a tomato soup" versions are "proper" English; they just express slightly different things. Sure, the former is more likely, but the latter is perfectly understandable and grammatically correct. Anyway, soup doesn't always come in bowls.
'I would like' is listed as possible meaning of 'voglio', and yet was marked 'wrong' when I used it in my answer. It's not the literally correct translation of 'voglio', but it is natural to say it in this context; presumably that's why it is listed!
Belianis. you are right. In italian "i want" does not exist. They use the polite form "i would want". It is a subjuntive. That is why there is an "i" extra in the word voglio. It comes from "volere" and normal grammar rules would make ï want" "volo", but that means "flight".