Apex domains cannot have CNAME records.
Question and response
Question
dig violleau-assurances.com. NS
Answer
violleau-assurances.com. 5 NS ns2.violleau-assurances.com.
violleau-assurances.com. 5 NS ns1.violleau-assurances.com.
Authority
The response has no authority records.
Additional
ns1.violleau-assurances.com. 5 A 107.6.155.82
ns2.violleau-assurances.com. 5 A 107.6.155.85
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0