Apex domains cannot have CNAME records.
Question and response
Question
dig koc.net. NS
Answer
koc.net. 5 NS coltrane.mgmt.koc.net.
koc.net. 5 NS dnsa1.vodafone.net.tr.
koc.net. 5 NS dizzy.mgmt.koc.net.
koc.net. 5 NS dnsa2.vodafone.net.tr.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0