Apex domains cannot have CNAME records.
Question and response
Question
dig 8.9.b.4.1.0.0.2.ip6.arpa. NS
Answer
8.9.b.4.1.0.0.2.ip6.arpa. 5 NS dns0.gandi.net.
8.9.b.4.1.0.0.2.ip6.arpa. 5 NS dns2.gandi.net.
8.9.b.4.1.0.0.2.ip6.arpa. 5 NS dns4.gandi.net.
8.9.b.4.1.0.0.2.ip6.arpa. 5 NS dns1.gandi.net.
8.9.b.4.1.0.0.2.ip6.arpa. 5 NS dns3.gandi.net.
Authority
The response has no authority records.
Additional
dns0.gandi.net. 5 A 217.70.177.39
dns1.gandi.net. 5 A 217.70.177.45
dns2.gandi.net. 5 A 217.70.183.211
dns3.gandi.net. 5 A 217.70.184.14
dns4.gandi.net. 5 A 217.70.186.184
dns0.gandi.net. 5 AAAA 2001:4b98:d:1:0:0:0:39
dns1.gandi.net. 5 AAAA 2001:4b98:d:1:0:0:0:45
dns2.gandi.net. 5 AAAA 2001:4b98:d:589:0:0:0:211
dns3.gandi.net. 5 AAAA 2001:4b98:c:13:0:0:0:14
dns4.gandi.net. 5 AAAA 2001:4b98:dc2:90:217:70:186:184
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0