Apex domains cannot have CNAME records.
Question and response
Question
dig seguroz.com.br. NS
Answer
seguroz.com.br. 5 NS walt.ns.cloudflare.com.
seguroz.com.br. 5 NS davina.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0