Apex domains cannot have CNAME records.
Question and response
Question
dig iwt.at. NS
Answer
iwt.at. 5 NS dns2.iwt.at.
iwt.at. 5 NS dns1.iwt.at.
iwt.at. 5 NS dns3.iwt.at.
Authority
The response has no authority records.
Additional
dns1.iwt.at. 5 A 109.237.142.8
dns2.iwt.at. 5 A 148.251.254.105
dns3.iwt.at. 5 A 109.237.143.8
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0