Apex domains cannot have CNAME records.
Question and response
Question
dig corpedia.com. NS
Answer
corpedia.com. 5 NS ns-1466.awsdns-55.org.
corpedia.com. 5 NS ns-89.awsdns-11.com.
corpedia.com. 5 NS ns-988.awsdns-59.net.
corpedia.com. 5 NS ns-1990.awsdns-56.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0