Apex domains cannot have CNAME records.
Question and response
Question
dig mxbeuc.freshdesk.com. NS
Answer
mxbeuc.freshdesk.com. 5 NS ns-1809.awsdns-34.co.uk.
mxbeuc.freshdesk.com. 5 NS ns-1292.awsdns-33.org.
mxbeuc.freshdesk.com. 5 NS ns-105.awsdns-13.com.
mxbeuc.freshdesk.com. 5 NS ns-965.awsdns-56.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0