Apex domains cannot have CNAME records.
Question and response
Question
dig ess.in.barracudanetworks.com. NS
Answer
ess.in.barracudanetworks.com. 5 NS ns-168.awsdns-21.com.
ess.in.barracudanetworks.com. 5 NS ns-1508.awsdns-60.org.
ess.in.barracudanetworks.com. 5 NS ns-533.awsdns-02.net.
ess.in.barracudanetworks.com. 5 NS ns-1654.awsdns-14.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0