Apex domains cannot have CNAME records.
Question and response
Question
dig ikb.at. NS
Answer
ikb.at. 5 NS ns2.ikbnet.co.at.
ikb.at. 5 NS ns6.ikbnet.at.
ikb.at. 5 NS ns1.ikbnet.co.at.
Authority
The response has no authority records.
Additional
ns6.ikbnet.at. 5 A 146.185.92.81
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0