Apex domains cannot have CNAME records.
Question and response
Question
dig mls.com.br. NS
Answer
mls.com.br. 5 NS ns4.mls.com.br.
mls.com.br. 5 NS ns2.mls.com.br.
mls.com.br. 5 NS ns.mls.com.br.
mls.com.br. 5 NS ns3.mls.com.br.
Authority
The response has no authority records.
Additional
ns.mls.com.br. 5 A 200.152.96.5
ns2.mls.com.br. 5 A 200.152.96.2
ns3.mls.com.br. 5 A 200.152.98.2
ns4.mls.com.br. 5 A 200.152.98.5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0