Apex domains cannot have CNAME records.
Question and response
Question
dig cittatelecom.net.br. NS
Answer
cittatelecom.net.br. 5 NS ns1.cittatelecom.net.br.
cittatelecom.net.br. 5 NS ns2.cittatelecom.net.br.
Authority
The response has no authority records.
Additional
ns1.cittatelecom.net.br. 5 A 177.129.8.111
ns2.cittatelecom.net.br. 5 A 177.129.8.112
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0