Apex domains cannot have CNAME records.
Question and response
Question
dig freshservice.com. NS
Answer
freshservice.com. 5 NS ns-1687.awsdns-18.co.uk.
freshservice.com. 5 NS ns-566.awsdns-06.net.
freshservice.com. 5 NS ns-302.awsdns-37.com.
freshservice.com. 5 NS ns-1410.awsdns-48.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0