Apex domains cannot have CNAME records.
Question and response
Question
dig medienservice.de. NS
Answer
medienservice.de. 5 NS anycast2.irondns.net.
medienservice.de. 5 NS anycast1.irondns.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0