Apex domains cannot have CNAME records.
Question and response
Question
dig ghostgate.de. NS
Answer
ghostgate.de. 4 NS dns2.ghostnet.de.
ghostgate.de. 4 NS dns4.ghostnet.de.
ghostgate.de. 4 NS dns1.ghostnet.de.
ghostgate.de. 4 NS dns3.ghostnet.de.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0