Apex domains cannot have CNAME records.
Question and response
Question
dig isotelecom.com. NS
Answer
isotelecom.com. 5 NS dns2.namebay.com.
isotelecom.com. 5 NS dns1.namebay.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0