Apex domains cannot have CNAME records.
Question and response
Question
dig ess.ca.barracudanetworks.com. NS
Answer
ess.ca.barracudanetworks.com. 5 NS ns-1377.awsdns-44.org.
ess.ca.barracudanetworks.com. 5 NS ns-1952.awsdns-52.co.uk.
ess.ca.barracudanetworks.com. 5 NS ns-92.awsdns-11.com.
ess.ca.barracudanetworks.com. 5 NS ns-528.awsdns-02.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0