Apex domains cannot have CNAME records.
Question and response
Question
dig static.gvt.net.br. NS
Answer
static.gvt.net.br. 5 NS dns4.gvt.net.br.
static.gvt.net.br. 5 NS dns1.gvt.net.br.
static.gvt.net.br. 5 NS dns2.gvt.net.br.
static.gvt.net.br. 5 NS dns3.gvt.net.br.
Authority
The response has no authority records.
Additional
dns1.gvt.net.br. 4 A 200.146.72.5
dns2.gvt.net.br. 4 A 200.139.125.38
dns3.gvt.net.br. 4 A 186.215.69.150
dns4.gvt.net.br. 4 A 177.43.193.61
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0