Apex domains cannot have CNAME records.
Question and response
Question
dig opcnet.hu. NS
Answer
opcnet.hu. 5 NS ns3.opcnet.hu.
opcnet.hu. 5 NS ns4.opcnet.hu.
Authority
The response has no authority records.
Additional
ns3.opcnet.hu. 5 A 85.90.160.70
ns4.opcnet.hu. 5 A 85.90.166.155
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0