Apex domains cannot have CNAME records.
Question and response
Question
dig redebrtelecom.com.br. NS
Answer
redebrtelecom.com.br. 3 NS ns3.locaweb.com.br.
redebrtelecom.com.br. 3 NS ns2.locaweb.com.br.
redebrtelecom.com.br. 3 NS ns1.locaweb.com.br.
Authority
The response has no authority records.
Additional
ns1.locaweb.com.br. 3 A 186.202.8.254
ns2.locaweb.com.br. 3 A 187.45.248.254
ns3.locaweb.com.br. 3 A 189.126.101.254
ns1.locaweb.com.br. 3 AAAA 2804:218:7000:0:186:202:8:254
ns2.locaweb.com.br. 3 AAAA 2804:218:7001:0:187:45:248:254
ns3.locaweb.com.br. 3 AAAA 2804:218:7002:0:189:126:101:254
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0