Apex domains cannot have CNAME records.
Question and response
Question
dig nicdirect.de. NS
Answer
nicdirect.de. 5 NS ns1.dnsresolve.net.
nicdirect.de. 5 NS ns2.dnsresolve.net.
Authority
The response has no authority records.
Additional
ns1.dnsresolve.net. 5 A 193.254.184.231
ns2.dnsresolve.net. 5 A 193.254.185.231
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0