Apex domains cannot have CNAME records.
Question and response
Question
dig dnsonly.cray.com.br. NS
Answer
dnsonly.cray.com.br. 5 NS ns3.cray.com.br.
dnsonly.cray.com.br. 5 NS b.ns.cipnet.com.br.
dnsonly.cray.com.br. 5 NS a.ns.cipnet.com.br.
dnsonly.cray.com.br. 5 NS ns4.cray.com.br.
Authority
The response has no authority records.
Additional
a.ns.cipnet.com.br. 5 A 200.219.229.119
b.ns.cipnet.com.br. 5 A 67.205.184.65
ns3.cray.com.br. 5 A 200.219.229.119
ns4.cray.com.br. 5 A 67.205.184.65
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0