Apex domains cannot have CNAME records.
Question and response
Question
dig sys.sulinet.hu. NS
Answer
sys.sulinet.hu. 5 NS ns2.sztaki.hbone.hu.
sys.sulinet.hu. 5 NS ns2.iif.hu.
Authority
The response has no authority records.
Additional
ns2.iif.hu. 5 A 193.225.12.59
ns2.sztaki.hbone.hu. 5 A 193.225.13.116
ns2.sztaki.hbone.hu. 5 AAAA 2001:738:0:302:0:0:0:116
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0