Apex domains cannot have CNAME records.
Question and response
Question
dig arz.at. NS
Answer
arz.at. 5 NS nsi2.arz.at.
arz.at. 5 NS nsi1.arz.at.
Authority
The response has no authority records.
Additional
nsi1.arz.at. 5 A 193.110.183.37
nsi2.arz.at. 5 A 193.110.182.37
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0