Apex domains cannot have CNAME records.
Question and response
Question
dig laboxy.fr. NS
Answer
laboxy.fr. 4 NS dns108.ovh.net.
laboxy.fr. 4 NS ns108.ovh.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0