Apex domains cannot have CNAME records.
Question and response
Question
dig optics-vision.gr. NS
Answer
optics-vision.gr. 5 NS dns1.papaki.gr.
optics-vision.gr. 5 NS dns2.papaki.gr.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0