Apex domains cannot have CNAME records.
Question and response
Question
dig dialhost.com.br. NS
Answer
dialhost.com.br. 4 NS ns2.dialhost.com.br.
dialhost.com.br. 4 NS ns4.dialhost.com.br.
dialhost.com.br. 4 NS ns1.dialhost.com.br.
dialhost.com.br. 4 NS ns3.dialhost.com.br.
Authority
The response has no authority records.
Additional
ns1.dialhost.com.br. 4 A 177.52.162.91
ns2.dialhost.com.br. 4 A 138.118.174.247
ns3.dialhost.com.br. 4 A 45.42.162.8
ns4.dialhost.com.br. 4 A 187.102.244.6
ns1.dialhost.com.br. 4 AAAA 2804:b44:a000:0:0:0:0:f
ns2.dialhost.com.br. 4 AAAA 2804:b44:a000:0:0:0:0:44
ns3.dialhost.com.br. 4 AAAA 2602:fa0e:1:10:0:0:884b:d626
ns4.dialhost.com.br. 4 AAAA 2804:b44:a000:0:0:0:0:4a
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0