Apex domains cannot have CNAME records.
Question and response
Question
dig idc.telekom.hu. NS
Answer
idc.telekom.hu. 5 NS ans1.telekom.hu.
idc.telekom.hu. 5 NS ans2.telekom.hu.
idc.telekom.hu. 5 NS ns1.idc.telekom.hu.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0