Apex domains cannot have CNAME records.
Question and response
Question
dig thinkwhy.com. NS
Answer
thinkwhy.com. 5 NS ns-404.awsdns-50.com.
thinkwhy.com. 5 NS ns-1348.awsdns-40.org.
thinkwhy.com. 5 NS ns-892.awsdns-47.net.
thinkwhy.com. 5 NS ns-1581.awsdns-05.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0