Apex domains cannot have CNAME records.
Question and response
Question
dig nuxoa.de. NS
Answer
nuxoa.de. 5 NS cortney.ns.cloudflare.com.
nuxoa.de. 5 NS john.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0