Apex domains cannot have CNAME records.
Question and response
Question
dig bundesverband-gutachter.de. NS
Answer
bundesverband-gutachter.de. 5 NS lvps83-169-2-34.dedicated.hosteurope.de.
bundesverband-gutachter.de. 5 NS pdns02.domaincontrol.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0