ns.duohemoglobin.com has no CNAME records.
Question and response
Question
dig ns.duohemoglobin.com. NS
Answer
The response has no answer records.
Authority
duohemoglobin.com. 8681 SOA ns.duohemoglobin.com. kiki\.kwad.gmail.com. 1769616822 10800 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0