Apex domains cannot have CNAME records.
Question and response
Question
dig ansp.br. NS
Answer
ansp.br. 5 NS ns3.ansp.br.
ansp.br. 5 NS ns2.ansp.br.
ansp.br. 5 NS ns1.ansp.br.
Authority
The response has no authority records.
Additional
ns1.ansp.br. 5 A 143.108.30.90
ns2.ansp.br. 5 A 143.108.30.3
ns3.ansp.br. 5 A 200.145.6.87
ns1.ansp.br. 5 AAAA 2001:12d8:88:30:0:0:0:2
ns2.ansp.br. 5 AAAA 2001:12d8:88:30:0:0:0:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0