Apex domains cannot have CNAME records.
Question and response
Question
dig proofhub.com. NS
Answer
proofhub.com. 5 NS ns-491.awsdns-61.com.
proofhub.com. 5 NS ns-1267.awsdns-30.org.
proofhub.com. 5 NS ns-772.awsdns-32.net.
proofhub.com. 5 NS ns-1566.awsdns-03.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0