Apex domains cannot have CNAME records.
Question and response
Question
dig mgdis.fr. NS
Answer
mgdis.fr. 1 NS ns1109.ui-dns.de.
mgdis.fr. 1 NS ns1109.ui-dns.org.
mgdis.fr. 1 NS ns1109.ui-dns.com.
mgdis.fr. 1 NS ns1109.ui-dns.biz.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0