Apex domains cannot have CNAME records.
Question and response
Question
dig secure-shield.at. NS
Answer
secure-shield.at. 5 NS ns3.abaton.at.
secure-shield.at. 5 NS ns2.abaton.at.
secure-shield.at. 5 NS ns1.abaton.at.
Authority
The response has no authority records.
Additional
ns1.abaton.at. 5 A 193.200.113.113
ns2.abaton.at. 5 A 94.247.144.14
ns3.abaton.at. 5 A 91.216.247.250
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0