Apex domains cannot have CNAME records.
Question and response
Question
dig petton.fr. NS
Answer
petton.fr. 1 NS dns110.ovh.net.
petton.fr. 1 NS ns110.ovh.net.
Authority
The response has no authority records.
Additional
ns110.ovh.net. 2 A 5.135.78.233
dns110.ovh.net. 2 A 5.196.44.1
ns110.ovh.net. 2 AAAA 2001:41d0:b00:fe00:0:0:0:2
dns110.ovh.net. 2 AAAA 2001:41d0:d01:400:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0