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