Apex domains cannot have CNAME records.
Question and response
Question
dig freshcaller.com. NS
Answer
freshcaller.com. 5 NS ns-732.awsdns-27.net.
freshcaller.com. 5 NS ns-1098.awsdns-09.org.
freshcaller.com. 5 NS ns-1936.awsdns-50.co.uk.
freshcaller.com. 5 NS ns-183.awsdns-22.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0