Apex domains cannot have CNAME records.
Question and response
Question
dig saofrancisco.edu.br. NS
Answer
saofrancisco.edu.br. 5 NS ns2-04.azure-dns.net.
saofrancisco.edu.br. 5 NS ns1-04.azure-dns.com.
saofrancisco.edu.br. 5 NS ns4-04.azure-dns.info.
saofrancisco.edu.br. 5 NS ns3-04.azure-dns.org.
Authority
The response has no authority records.
Additional
ns1-04.azure-dns.com. 5 A 13.107.236.4
ns2-04.azure-dns.net. 5 A 150.171.21.4
ns4-04.azure-dns.info. 2 A 208.84.5.4
ns1-04.azure-dns.com. 5 AAAA 2603:1061:0:700:0:0:0:4
ns2-04.azure-dns.net. 5 AAAA 2620:1ec:8ec:700:0:0:0:4
ns4-04.azure-dns.info. 2 AAAA 2620:1ec:bda:700:0:0:0:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0