Apex domains cannot have CNAME records.
Question and response
Question
dig fcmproductions.com. NS
Answer
fcmproductions.com. 3 NS maceio.ns.porkbun.com.
fcmproductions.com. 3 NS fortaleza.ns.porkbun.com.
fcmproductions.com. 3 NS salvador.ns.porkbun.com.
fcmproductions.com. 3 NS curitiba.ns.porkbun.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0