Apex domains cannot have CNAME records.
Question and response
Question
dig hosteam.fr. NS
Answer
hosteam.fr. 5 NS ns3.cyres.fr.
hosteam.fr. 5 NS ns2.cyres.fr.
hosteam.fr. 5 NS ns1.cyres.fr.
Authority
The response has no authority records.
Additional
ns1.cyres.fr. 5 A 91.206.156.73
ns2.cyres.fr. 5 A 154.41.65.85
ns3.cyres.fr. 5 A 185.90.99.49
ns1.cyres.fr. 5 AAAA 2a05:df00:0:149:172:31:36:40
ns2.cyres.fr. 5 AAAA 2001:978:5a01:5:172:31:36:41
ns3.cyres.fr. 5 AAAA 2a05:df00:0:149:185:90:99:49
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0