Apex domains cannot have CNAME records.
Question and response
Question
dig kertel.com. NS
Answer
kertel.com. 5 NS ns-39-a.gandi.net.
kertel.com. 5 NS ns-194-b.gandi.net.
kertel.com. 5 NS ns-160-c.gandi.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0