Apex domains cannot have CNAME records.
Question and response
Question
dig arinsights.com. NS
Answer
arinsights.com. 5 NS ns-273.awsdns-34.com.
arinsights.com. 5 NS ns-1074.awsdns-06.org.
arinsights.com. 5 NS ns-942.awsdns-53.net.
arinsights.com. 5 NS ns-1732.awsdns-24.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0