Apex domains cannot have CNAME records.
Question and response
Question
dig hkdogo.com. NS
Answer
hkdogo.com. 5 NS ns-2001.awsdns-58.co.uk.
hkdogo.com. 5 NS ns-1140.awsdns-14.org.
hkdogo.com. 5 NS ns-943.awsdns-53.net.
hkdogo.com. 5 NS ns-1374.awsdns-43.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0