Apex domains cannot have CNAME records.
Question and response
Question
dig cretaforce.gr. NS
Answer
cretaforce.gr. 5 NS ns1.cretaforce.gr.
cretaforce.gr. 5 NS ns0.cretaforce.gr.
cretaforce.gr. 5 NS ns2.cretaforce.gr.
Authority
The response has no authority records.
Additional
ns0.cretaforce.gr. 5 A 195.201.97.99
ns1.cretaforce.gr. 5 A 94.130.217.104
ns2.cretaforce.gr. 5 A 94.130.217.87
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0