Apex domains cannot have CNAME records.
Question and response
Question
dig digital-services.at. NS
Answer
digital-services.at. 1 NS nsz.fueber.org.
digital-services.at. 1 NS nsx.fueber.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0