Apex domains cannot have CNAME records.
Question and response
Question
dig zaapnet.com.br. NS
Answer
zaapnet.com.br. 5 NS a.dns.mantenedora.io.
zaapnet.com.br. 5 NS ns01.zaapnet.com.br.
zaapnet.com.br. 5 NS b.dns.mantenedora.io.
zaapnet.com.br. 5 NS ns02.zaapnet.com.br.
Authority
The response has no authority records.
Additional
ns01.zaapnet.com.br. 5 A 168.90.59.3
ns02.zaapnet.com.br. 5 A 168.90.59.4
ns01.zaapnet.com.br. 5 AAAA 2804:2d60:7000:0:0:0:0:20
ns02.zaapnet.com.br. 5 AAAA 2804:2d60:f000:0:0:0:0:20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0