Apex domains cannot have CNAME records.
Question and response
Question
dig bbox.fr. NS
Answer
bbox.fr. 5 NS ns2.bouyguesbox.fr.
bbox.fr. 5 NS nsb.perf1.com.
bbox.fr. 5 NS nsa.perf1.fr.
bbox.fr. 5 NS ns1.bouyguesbox.fr.
bbox.fr. 5 NS nsc.perf1.com.
Authority
The response has no authority records.
Additional
ns1.bouyguesbox.fr. 5 A 194.158.122.53
ns2.bouyguesbox.fr. 5 A 194.158.123.53
nsa.perf1.fr. 5 A 81.92.94.100
nsb.perf1.com. 5 A 81.92.95.100
nsc.perf1.com. 5 A 152.89.172.100
ns1.bouyguesbox.fr. 5 AAAA 2001:864:f009:1:0:0:0:d1
ns2.bouyguesbox.fr. 5 AAAA 2001:864:f003:1:0:0:0:d1
nsa.perf1.fr. 5 AAAA 2a01:c8:100:0:0:0:0:100
nsb.perf1.com. 5 AAAA 2a01:c8:101:0:0:0:0:100
nsc.perf1.com. 5 AAAA 2a09:35c0:102:0:0:0:0:100
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0