nightmare.medatec.de has no CNAME records.
Question and response
Question
dig nightmare.medatec.de. NS
Answer
The response has no answer records.
Authority
medatec.de. 1952 SOA dns1.registrar-servers.com. hostmaster.registrar-servers.com. 1773066849 43200 3600 604800 3601
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0