Apex domains cannot have CNAME records.
Question and response
Question
dig ns3.zomro.com. NS
Answer
ns3.zomro.com. 5 NS ns1.omro.host.
ns3.zomro.com. 5 NS ns2.omro.info.
ns3.zomro.com. 5 NS ns3.omro.cc.
ns3.zomro.com. 5 NS ns4.omro.in.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0