Apex domains cannot have CNAME records.
Question and response
Question
dig dus8.dedicated.server-hosting.expert. NS
Answer
dus8.dedicated.server-hosting.expert. 2 NS ns2.ntdns.de.
dus8.dedicated.server-hosting.expert. 2 NS ns3.ntdns.de.
dus8.dedicated.server-hosting.expert. 2 NS ns1.ntdns.de.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0