b-dns.PL has no CNAME records.
Question and response
Question
dig b-dns.PL. NS
Answer
The response has no answer records.
Authority
PL. 3136 SOA a-dns.PL. dnsmaster.nask.PL. 1771979703 900 300 2592000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0