Apex domains cannot have CNAME records.
Question and response
Question
dig isp.hu. NS
Answer
isp.hu. 5 NS nsa2.isp.hu.
isp.hu. 5 NS nsa1.isp.hu.
Authority
The response has no authority records.
Additional
nsa1.isp.hu. 5 A 62.77.203.11
nsa2.isp.hu. 5 A 213.163.34.67
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0