Apex domains cannot have CNAME records.
Question and response
Question
dig nippontec.net. NS
Answer
nippontec.net. 5 NS nsa4.k8.com.br.
nippontec.net. 5 NS nsa6.k8.com.br.
nippontec.net. 5 NS nsa2.k8.com.br.
nippontec.net. 5 NS nsa1.k8.com.br.
nippontec.net. 5 NS nsa3.k8.com.br.
nippontec.net. 5 NS nsa5.k8.com.br.
Authority
The response has no authority records.
Additional
nsa1.k8.com.br. 5 A 24.199.64.26
nsa2.k8.com.br. 5 A 177.71.180.90
nsa3.k8.com.br. 5 A 24.199.64.101
nsa4.k8.com.br. 5 A 79.125.16.81
nsa5.k8.com.br. 5 A 45.55.108.139
nsa6.k8.com.br. 5 A 184.73.203.216
nsa1.k8.com.br. 5 AAAA 2604:a880:400:d0:0:0:2371:2001
nsa2.k8.com.br. 5 AAAA 2600:1f1e:f14:a800:fea2:3e55:175:8c9a
nsa3.k8.com.br. 5 AAAA 2604:a880:400:d0:0:0:1a8f:e001
nsa4.k8.com.br. 5 AAAA 2a05:d018:eef:900:733d:f263:b144:cf6a
nsa5.k8.com.br. 5 AAAA 2604:a880:1:20:0:0:5a:8001
nsa6.k8.com.br. 5 AAAA 2600:1f18:73e:d500:821c:da38:5464:b4ee
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0