Apex domains cannot have CNAME records.
Question and response
Question
dig tmkultra.net.br. NS
Answer
tmkultra.net.br. 2 NS ns2.tmkultra.net.br.
tmkultra.net.br. 2 NS ns1.tmkultra.net.br.
Authority
The response has no authority records.
Additional
ns1.tmkultra.net.br. 2 A 170.84.104.255
ns2.tmkultra.net.br. 2 A 170.84.106.255
ns1.tmkultra.net.br. 2 AAAA 2804:318c:f:d:0:0:104:255
ns2.tmkultra.net.br. 2 AAAA 2804:318c:f000:d:0:0:106:255
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0