Apex domains cannot have CNAME records.
Question and response
Question
dig addonline.fr. NS
Answer
addonline.fr. 5 NS ns1.add-online.com.
addonline.fr. 5 NS ns2.add-online.com.
Authority
The response has no authority records.
Additional
ns1.add-online.com. 5 A 195.28.200.101
ns2.add-online.com. 5 A 178.23.155.191
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0