Apex domains cannot have CNAME records.
Question and response
Question
dig shm200.egg.jp. NS
Answer
shm200.egg.jp. 5 NS ns03.idcfcloud.com.
shm200.egg.jp. 5 NS ns01.idcfcloud.com.
shm200.egg.jp. 5 NS ns02.idcfcloud.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0