Apex domains cannot have CNAME records.
Question and response
Question
dig cnmss.fr. NS
Answer
cnmss.fr. 1 NS ns1-a.nadns1.fr.
cnmss.fr. 1 NS ns1-c.nadns1.com.
cnmss.fr. 1 NS ns1-b.nadns1.com.
Authority
The response has no authority records.
Additional
ns1-a.nadns1.fr. 1 A 81.92.91.146
ns1-a.nadns1.fr. 1 A 185.65.58.146
ns1-b.nadns1.com. 1 A 45.76.37.152
ns1-b.nadns1.com. 1 A 169.150.255.36
ns1-c.nadns1.com. 1 A 45.77.155.69
ns1-c.nadns1.com. 1 A 121.127.42.113
ns1-a.nadns1.fr. 1 AAAA 2a01:c8:200:111:0:0:0:146
ns1-a.nadns1.fr. 1 AAAA 2a01:c8:300:111:0:0:0:146
ns1-b.nadns1.com. 1 AAAA 2001:19f0:5001:3b57:0:0:0:152
ns1-b.nadns1.com. 1 AAAA 2a02:6ea0:c776:1:0:0:0:36
ns1-c.nadns1.com. 1 AAAA 2001:19f0:5:3150:0:0:0:69
ns1-c.nadns1.com. 1 AAAA 2a02:6ea0:e216:1:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0