"Who is the president?"
As far as my knowledge of the language goes, it is unless there was a very special way that you needed to change the stress. The best way to think about how to form questions in Turkish is to imagine how you would ask the question in shock ("The president is WHO?!).
"Who is the president?" Translation: Başkan kim?
"Başkan kimdir?" Başka doğru Türkçe cevap. Correct other Turkish answer.
What is the meaning of "başkan kimdir?" The meaning is the same & the -dir suffix is optional in this example.
You will find other examples on Duo that use the -dir suffix as being required.
Added after a noun or adjective to mean (he/she/it) "is" (or are).
Kim? a question pronoun meaning "who?"
Kimdir? "who is?"