Apex domains cannot have CNAME records.
Question and response
Question
dig vodafone.com.tr. NS
Answer
vodafone.com.tr. 5 NS ns1.vodafone.com.tr.
vodafone.com.tr. 5 NS ns2.vodafone.com.tr.
vodafone.com.tr. 5 NS ns3.vodafone.com.tr.
Authority
The response has no authority records.
Additional
ns1.vodafone.com.tr. 5 A 212.65.128.1
ns2.vodafone.com.tr. 5 A 212.65.129.1
ns3.vodafone.com.tr. 5 A 212.65.130.1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0