Apex domains cannot have CNAME records.
Question and response
Question
dig sosafe.de. NS
Answer
sosafe.de. 5 NS ns-2015.awsdns-59.co.uk.
sosafe.de. 5 NS ns-612.awsdns-12.net.
sosafe.de. 5 NS ns-115.awsdns-14.com.
sosafe.de. 5 NS ns-1333.awsdns-38.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0