"What are you doing?"
Translation:Kamu sedang apa?
Yes, you could possibly, but it depends on what else is going on in the sentence you make. You could say /Apakah yang dilakukan oleh kamu?/ but it would probably be more common to use /Apakah yang kamu lakukan?/ instead. For personal pronouns with passive verbs inside a /yang/ statement, the /di-/ is dropped and the personal pronoun is fronted immediately before the verb (and after any helping/modal verbs).