b.xnameserver.de has no CNAME records.
Question and response
Question
dig b.xnameserver.de. NS
Answer
The response has no answer records.
Authority
xnameserver.de. 3161 SOA a.xnameserver.de. hostmaster.xnameserver.de. 2022062902 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0