Apex domains cannot have CNAME records.
Question and response
Question
dig vautron.de. NS
Answer
vautron.de. 5 NS nsx.nsserve.de.
vautron.de. 5 NS nsx.ns-serve.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0