Apex domains cannot have CNAME records.
Question and response
Question
dig sztaki.hu. NS
Answer
sztaki.hu. 5 NS ns5.univie.ac.at.
sztaki.hu. 5 NS ns4.sztaki.hu.
sztaki.hu. 5 NS nic.bme.hu.
Authority
The response has no authority records.
Additional
nic.bme.hu. 5 A 152.66.115.1
ns4.sztaki.hu. 5 A 193.6.200.130
ns5.univie.ac.at. 5 A 193.171.255.77
nic.bme.hu. 5 AAAA 2001:738:2001:2001:0:0:0:2
ns5.univie.ac.at. 5 AAAA 2001:628:453:4305:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0