Apex domains cannot have CNAME records.
Question and response
Question
dig simexo04.net. NS
Answer
simexo04.net. 5 NS sdns2.ovh.net.
simexo04.net. 5 NS ns.simexo04.net.
Authority
The response has no authority records.
Additional
ns.simexo04.net. 5 A 87.98.132.111
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0