Apex domains cannot have CNAME records.
Question and response
Question
dig as212027.host. NS
Answer
as212027.host. 2 NS curitiba.ns.porkbun.com.
as212027.host. 2 NS maceio.ns.porkbun.com.
as212027.host. 2 NS fortaleza.ns.porkbun.com.
as212027.host. 2 NS salvador.ns.porkbun.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0