Apex domains cannot have CNAME records.
Question and response
Question
dig tosspayments.com. NS
Answer
tosspayments.com. 5 NS ns-216.awsdns-27.com.
tosspayments.com. 5 NS ns-1909.awsdns-46.co.uk.
tosspayments.com. 5 NS ns-1420.awsdns-49.org.
tosspayments.com. 5 NS ns-826.awsdns-39.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0