Apex domains cannot have CNAME records.
Question and response
Question
dig isgroup.info. NS
Answer
isgroup.info. 5 NS tina.ns.cloudflare.com.
isgroup.info. 5 NS newt.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0