Apex domains cannot have CNAME records.
Question and response
Question
dig ote.gr. NS
Answer
ote.gr. 5 NS dns.ote.gr.
ote.gr. 5 NS dns1.ote.gr.
Authority
The response has no authority records.
Additional
dns.ote.gr. 5 A 195.167.52.2
dns1.ote.gr. 5 A 212.205.80.29
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0