"Você tem certeza?"

Translation: Are you sure?

[DaleNixon]

I went very literal but "Do you have certainty" should be valid

[hkysonjr]

"Are you certain" is also a valid translation of this sentence.

[chribing]

Should "You are certain?" also be acceptable if "Are you certain?" is?

[Oporto2015]

Yes, in fact this is how they ask questions in Portugal all the time. Are you certain? should be accepted.