Apex domains cannot have CNAME records.
Question and response
Question
dig 4.5.a.0.4.0.8.2.ip6.arpa. NS
Answer
4.5.a.0.4.0.8.2.ip6.arpa. 5 NS ns01.leste.com.br.4.5.a.0.4.0.8.2.ip6.arpa.
4.5.a.0.4.0.8.2.ip6.arpa. 5 NS ns02.leste.com.br.4.5.a.0.4.0.8.2.ip6.arpa.
4.5.a.0.4.0.8.2.ip6.arpa. 5 NS ns03.leste.com.br.4.5.a.0.4.0.8.2.ip6.arpa.
4.5.a.0.4.0.8.2.ip6.arpa. 5 NS ns04.leste.com.br.4.5.a.0.4.0.8.2.ip6.arpa.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0