Apex domains cannot have CNAME records.
Question and response
Question
dig ultraveloztelecom.com.br. NS
Answer
ultraveloztelecom.com.br. 4 NS ns2.ultraveloztelecom.com.br.
ultraveloztelecom.com.br. 4 NS ns1.ultraveloztelecom.com.br.
Authority
The response has no authority records.
Additional
ns1.ultraveloztelecom.com.br. 4 A 186.233.26.254
ns2.ultraveloztelecom.com.br. 4 A 186.233.26.253
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0