Apex domains cannot have CNAME records.
Question and response
Question
dig dns1.iscgnet.com. NS
Answer
dns1.iscgnet.com. 5 NS ns1.66-242-35-30.cprapid.com.
dns1.iscgnet.com. 5 NS ns2.66-242-35-30.cprapid.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0