Apex domains cannot have CNAME records.
Question and response
Question
dig nshost2.de. NS
Answer
nshost2.de. 5 NS ns2.nshost2.de.
nshost2.de. 5 NS ns3.nshost2.net.
nshost2.de. 5 NS ns1.nshost2.de.
Authority
The response has no authority records.
Additional
ns1.nshost2.de. 5 A 89.107.184.116
ns2.nshost2.de. 5 A 89.107.185.20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0