Apex domains cannot have CNAME records.
Question and response
Question
dig serverprofi24.de. NS
Answer
serverprofi24.de. 1 NS ns5.nameserverservice.de.
serverprofi24.de. 1 NS ns6.nameserverservice.de.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0