Apex domains cannot have CNAME records.
Question and response
Question
dig acelia-habitat.fr. NS
Answer
acelia-habitat.fr. 5 NS ivan.ns.cloudflare.com.
acelia-habitat.fr. 5 NS vida.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0