Apex domains cannot have CNAME records.
Question and response
Question
dig mercadopago.com.br. NS
Answer
mercadopago.com.br. 5 NS ns-258.awsdns-32.com.
mercadopago.com.br. 5 NS ns-1517.awsdns-61.org.
mercadopago.com.br. 5 NS ns-987.awsdns-59.net.
mercadopago.com.br. 5 NS ns-1699.awsdns-20.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0