Apex domains cannot have CNAME records.
Question and response
Question
dig dns4.hu. NS
Answer
dns4.hu. 4 NS dns3.hu.
dns4.hu. 4 NS dns1.hu.
dns4.hu. 4 NS sec1.rcode0.net.
dns4.hu. 4 NS sec2.rcode0.net.
dns4.hu. 4 NS dns2.hu.
dns4.hu. 4 NS dns4.hu.
Authority
The response has no authority records.
Additional
dns4.hu. 4 A 213.181.220.14
sec1.rcode0.net. 3 A 192.174.68.100
sec2.rcode0.net. 3 A 176.97.158.100
sec1.rcode0.net. 3 AAAA 2001:67c:1bc:0:0:0:0:100
sec2.rcode0.net. 3 AAAA 2001:67c:10b8:0:0:0:0:100
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0