slave.btcl.net.bd has no CNAME records.
Question and response
Question
dig slave.btcl.net.bd. NS
Answer
The response has no answer records.
Authority
btcl.net.bd. 398 SOA dns.btcl.net.bd. slave.btcl.net.bd. 2023061928 1200 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0