Apex domains cannot have CNAME records.
Question and response
Question
dig si.ikoula.net. NS
Answer
si.ikoula.net. 5 NS paul.ns.ikoula.com.
si.ikoula.net. 5 NS laura.ns.ikoula.com.
si.ikoula.net. 5 NS tristan.ns.ikoula.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0