Apex domains cannot have CNAME records.
Question and response
Question
dig z-net.hu. NS
Answer
z-net.hu. 5 NS ns2.zt.hu.
z-net.hu. 5 NS ns1.zt.hu.
Authority
The response has no authority records.
Additional
ns1.zt.hu. 5 A 185.106.112.230
ns2.zt.hu. 5 A 185.106.115.230
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0