Apex domains cannot have CNAME records.
Question and response
Question
dig itau.com.br. NS
Answer
itau.com.br. 5 NS usw2.akam.net.
itau.com.br. 5 NS usw6.akam.net.
itau.com.br. 5 NS asia1.akam.net.
itau.com.br. 5 NS ns1-127.akam.net.
itau.com.br. 5 NS ns1-88.akam.net.
itau.com.br. 5 NS usw1.akam.net.
itau.com.br. 5 NS use5.akam.net.
itau.com.br. 5 NS asia3.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0