Apex domains cannot have CNAME records.
Question and response
Question
dig grita.fr. NS
Answer
grita.fr. 5 NS ns-244-b.gandi.net.
grita.fr. 5 NS ns-167-c.gandi.net.
grita.fr. 5 NS ns-1-a.gandi.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0