Apex domains cannot have CNAME records.
Question and response
Question
dig arthuro256sh.com. NS
Answer
arthuro256sh.com. 5 NS ns-1418.awsdns-49.org.
arthuro256sh.com. 5 NS ns-1628.awsdns-11.co.uk.
arthuro256sh.com. 5 NS ns-178.awsdns-22.com.
arthuro256sh.com. 5 NS ns-1220.awsdns-24.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0