Apex domains cannot have CNAME records.
Question and response
Question
dig hosteurope.de. NS
Answer
hosteurope.de. 5 NS dns2.hosteurope.de.
hosteurope.de. 5 NS dns.hosteurope.de.
Authority
The response has no authority records.
Additional
dns.hosteurope.de. 5 A 80.237.128.156
dns2.hosteurope.de. 5 A 80.237.136.144
dns.hosteurope.de. 5 AAAA 2a01:488:0:0:0:0:0:35
dns2.hosteurope.de. 5 AAAA 2a01:488:0:0:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0