Apex domains cannot have CNAME records.
Question and response
Question
dig sip.com.tr. NS
Answer
sip.com.tr. 5 NS clayton.ns.cloudflare.com.
sip.com.tr. 5 NS fay.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0