Apex domains cannot have CNAME records.
Question and response
Question
dig dnsdocloud.com. NS
Answer
dnsdocloud.com. 5 NS ns1.virtualns.net.
dnsdocloud.com. 5 NS ns2.virtualns.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0