backend.antagus.de has no CNAME records.
Question and response
Question
dig backend.antagus.de. NS
Answer
The response has no answer records.
Authority
antagus.de. 1895 SOA ns1.antagus.de. root.ns1.antagus.de. 1692803702 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0