Apex domains cannot have CNAME records.
Question and response
Question
dig ultehdatacenter.de. NS
Answer
ultehdatacenter.de. 2 NS elmo.ns.cloudflare.com.
ultehdatacenter.de. 2 NS mia.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0