Apex domains cannot have CNAME records.
Question and response
Question
dig cgi.COM. NS
Answer
cgi.COM. 2 NS ns1.bluecatdns.COM.
cgi.COM. 2 NS ns1.f5clouddns.COM.
cgi.COM. 2 NS ns2.f5clouddns.COM.
cgi.COM. 2 NS ns1.bluecatdns.net.
cgi.COM. 2 NS ns1.bluecatdns.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0