The phrase “ならでは” means “unique to” or “characteristic of.” In the context of the sentence, “このレストランならではの味わいを楽しんでください” means “Please enjoy the unique taste that is characteristic of this restaurant.” The correct reading and usage of the phrase in this context is “ならではの.”
ならでは: This is the correct phrase, meaning “unique to” or “characteristic of.”
ならば: This phrase means “if” or “in that case” and is used to introduce a hypothetical situation.
ならで: This is not a correct phrase in this context.
ならでも: This is not a correct phrase in this context.