Apex domains cannot have CNAME records.
Question and response
Question
dig cielo.com.br. NS
Answer
cielo.com.br. 5 NS a12-67.akam.net.
cielo.com.br. 5 NS a8-67.akam.net.
cielo.com.br. 5 NS a3-65.akam.net.
cielo.com.br. 5 NS a7-66.akam.net.
cielo.com.br. 5 NS a1-184.akam.net.
cielo.com.br. 5 NS a14-64.akam.net.
Authority
The response has no authority records.
Additional
a12-67.akam.net. 1 A 184.26.160.67
a12-67.akam.net. 1 AAAA 2600:1480:f000:0:0:0:0:43
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0