Apex domains cannot have CNAME records.
Question and response
Question
dig unisites.com.br. NS
Answer
unisites.com.br. 5 NS ns3312.icloudzinc.com.
unisites.com.br. 5 NS ns3310.icloudzinc.com.
unisites.com.br. 5 NS ns3311.icloudzinc.com.
unisites.com.br. 5 NS ns3313.icloudzinc.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0