Apex domains cannot have CNAME records.
Question and response
Question
dig codestack.org. NS
Answer
codestack.org. 5 NS ns-1010.awsdns-62.net.
codestack.org. 5 NS ns-1479.awsdns-56.org.
codestack.org. 5 NS ns-1899.awsdns-45.co.uk.
codestack.org. 5 NS ns-471.awsdns-58.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0