Apex domains cannot have CNAME records.
Question and response
Question
dig postaffiliatepro.com. NS
Answer
postaffiliatepro.com. 5 NS ns-756.awsdns-30.net.
postaffiliatepro.com. 5 NS ns-2046.awsdns-63.co.uk.
postaffiliatepro.com. 5 NS ns-247.awsdns-30.com.
postaffiliatepro.com. 5 NS ns-1088.awsdns-08.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0