Apex domains cannot have CNAME records.
Question and response
Question
dig sigaonmais.com.br. NS
Answer
sigaonmais.com.br. 5 NS lakas.ns.cloudflare.com.
sigaonmais.com.br. 5 NS emerie.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
lakas.ns.cloudflare.com. 3 A 108.162.193.194
lakas.ns.cloudflare.com. 3 A 172.64.33.194
lakas.ns.cloudflare.com. 3 A 173.245.59.194
emerie.ns.cloudflare.com. 3 A 108.162.194.115
emerie.ns.cloudflare.com. 3 A 162.159.38.115
emerie.ns.cloudflare.com. 3 A 172.64.34.115
lakas.ns.cloudflare.com. 3 AAAA 2606:4700:58:0:0:0:adf5:3bc2
lakas.ns.cloudflare.com. 3 AAAA 2803:f800:50:0:0:0:6ca2:c1c2
lakas.ns.cloudflare.com. 3 AAAA 2a06:98c1:50:0:0:0:ac40:21c2
emerie.ns.cloudflare.com. 3 AAAA 2606:4700:50:0:0:0:a29f:2673
emerie.ns.cloudflare.com. 3 AAAA 2803:f800:50:0:0:0:6ca2:c273
emerie.ns.cloudflare.com. 3 AAAA 2a06:98c1:50:0:0:0:ac40:2273
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0