Apex domains cannot have CNAME records.
Question and response
Question
dig safesrv.de. NS
Answer
safesrv.de. 5 NS ns-393.awsdns-49.com.
safesrv.de. 5 NS ns-1164.awsdns-17.org.
safesrv.de. 5 NS ns-645.awsdns-16.net.
safesrv.de. 5 NS ns-1647.awsdns-13.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0