Apex domains cannot have CNAME records.
Question and response
Question
dig ex10.biz. NS
Answer
ex10.biz. 4 NS prod01.ns.ikoula.com.
ex10.biz. 4 NS prod02.ns.ikoula.com.
ex10.biz. 4 NS prod03.ns.ikoula.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0