Apex domains cannot have CNAME records.
Question and response
Question
dig freshsales.io. NS
Answer
freshsales.io. 5 NS ns-916.awsdns-50.net.
freshsales.io. 5 NS ns-1795.awsdns-32.co.uk.
freshsales.io. 5 NS ns-10.awsdns-01.com.
freshsales.io. 5 NS ns-1196.awsdns-21.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0