For example we tolking about taste. Каково на вкус это блюдо? what taste does this dish have?(is it correct?:) I think it is like an old option of какой(каков), какая(какова), какое(каково) used rarely, maybe in books but not in speaking.

We use "какова " or "каков", for example, when we ask about profession: "What is your profession?" - "Какова ваша профессия?"/ "Кто вы по профессии?" There are a few ways of translation. Example: "What is your position (opinion)?" -"Какова ваша позиция?"/ "Каково ваше мнение?" I hope my answer will help you.