Apex domains cannot have CNAME records.
Question and response
Question
dig iristelsecurity.com. NS
Answer
iristelsecurity.com. 5 NS pdns104.ultradns.com.
iristelsecurity.com. 5 NS pdns104.ultradns.net.
iristelsecurity.com. 5 NS pdns104.ultradns.org.
iristelsecurity.com. 5 NS pdns104.ultradns.biz.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0