Apex domains cannot have CNAME records.
Question and response
Question
dig serasa.com.br. NS
Answer
serasa.com.br. 5 NS ns-1363.awsdns-42.org.
serasa.com.br. 5 NS maq01.serasa.com.br.
serasa.com.br. 5 NS ns-108.awsdns-13.com.
serasa.com.br. 5 NS ns-717.awsdns-25.net.
serasa.com.br. 5 NS segateway01.serasa.com.br.
serasa.com.br. 5 NS ns-1633.awsdns-12.co.uk.
Authority
The response has no authority records.
Additional
maq01.serasa.com.br. 5 A 200.245.207.57
segateway01.serasa.com.br. 5 A 200.245.207.56
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0