Apex domains cannot have CNAME records.
Question and response
Question
dig re. NS
Answer
re. 2 NS g.ext.nic.fr.
re. 2 NS d.nic.fr.
re. 2 NS f.ext.nic.fr.
Authority
The response has no authority records.
Additional
d.nic.fr. 165889 A 194.0.9.1
f.ext.nic.fr. 160516 A 194.146.106.46
g.ext.nic.fr. 116801 A 194.0.36.1
d.nic.fr. 165889 AAAA 2001:678:c:0:0:0:0:1
f.ext.nic.fr. 160516 AAAA 2001:67c:1010:11:0:0:0:53
g.ext.nic.fr. 116801 AAAA 2001:678:4c:0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0