Apex domains cannot have CNAME records.
Question and response
Question
dig gnuss.at. NS
Answer
gnuss.at. 5 NS dns1.ewerke.cc.
gnuss.at. 5 NS dns2.ewerke.cc.
Authority
The response has no authority records.
Additional
dns1.ewerke.cc. 5 A 87.236.112.11
dns2.ewerke.cc. 5 A 194.183.129.90
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0