Apex domains cannot have CNAME records.
Question and response
Question
dig triinet.net.do. NS
Answer
triinet.net.do. 5 NS dns3.midominio.do.
triinet.net.do. 5 NS dns1.midominio.do.
triinet.net.do. 5 NS dns2.midominio.do.
triinet.net.do. 5 NS dns4.midominio.do.
Authority
The response has no authority records.
Additional
dns1.midominio.do. 1 A 162.251.82.122
dns1.midominio.do. 1 A 162.251.82.123
dns1.midominio.do. 1 A 162.251.82.250
dns1.midominio.do. 1 A 162.251.82.251
dns2.midominio.do. 1 A 162.251.82.120
dns2.midominio.do. 1 A 162.251.82.121
dns2.midominio.do. 1 A 162.251.82.248
dns2.midominio.do. 1 A 162.251.82.249
dns3.midominio.do. 1 A 162.251.82.118
dns3.midominio.do. 1 A 162.251.82.119
dns3.midominio.do. 1 A 162.251.82.246
dns3.midominio.do. 1 A 162.251.82.247
dns4.midominio.do. 1 A 162.251.82.124
dns4.midominio.do. 1 A 162.251.82.125
dns4.midominio.do. 1 A 162.251.82.252
dns4.midominio.do. 1 A 162.251.82.253
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0