Apex domains cannot have CNAME records.
Question and response
Question
dig ird.fr. NS
Answer
ird.fr. 2 NS censvrns0001.ird.fr.
ird.fr. 2 NS censvrns0003.ird.fr.
Authority
The response has no authority records.
Additional
censvrns0001.ird.fr. 2 A 91.203.32.147
censvrns0003.ird.fr. 2 A 193.50.53.33
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0