Which word cooked started with a prefix?

The word "cooked" doesn't start with a prefix. It's a simple, stand-alone verb.

However, you might be thinking of words related to "cooked" that *do* have prefixes, like:

* Uncooked: The prefix "un-" means "not" or "the opposite of."

* Overcooked: The prefix "over-" means "too much" or "excessively."

* Undercooked: The prefix "under-" means "not enough" or "insufficiently."