Apex domains cannot have CNAME records.
Question and response
Question
dig freshdesk.com. NS
Answer
freshdesk.com. 5 NS ns-350.awsdns-43.com.
freshdesk.com. 5 NS ns-1955.awsdns-52.co.uk.
freshdesk.com. 5 NS ns-1270.awsdns-30.org.
freshdesk.com. 5 NS ns-514.awsdns-00.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0