Apex domains cannot have CNAME records.
Question and response
Question
dig cupnagoya.org. NS
Answer
cupnagoya.org. 1 NS ns-506.awsdns-63.com.
cupnagoya.org. 1 NS ns-1388.awsdns-45.org.
cupnagoya.org. 1 NS ns-279.awsdns-34.com.
cupnagoya.org. 1 NS ns-397.awsdns-49.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0