Apex domains cannot have CNAME records.
Question and response
Question
dig cornut.fr. NS
Answer
cornut.fr. 5 NS ns3.rmi.fr.
cornut.fr. 5 NS ns4.rmi.fr.
Authority
The response has no authority records.
Additional
ns3.rmi.fr. 5 A 212.51.161.18
ns4.rmi.fr. 5 A 212.51.185.2
ns3.rmi.fr. 5 AAAA 2a01:728:0:1:0:0:0:3
ns4.rmi.fr. 5 AAAA 2a01:728:0:2:0:0:0:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0