Apex domains cannot have CNAME records.
Question and response
Question
dig porkbun.com. NS
Answer
porkbun.com. 5 NS ns-586.awsdns-09.net.
porkbun.com. 5 NS ns-1328.awsdns-38.org.
porkbun.com. 5 NS ns-1982.awsdns-55.co.uk.
porkbun.com. 5 NS ns-199.awsdns-24.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0