Apex domains cannot have CNAME records.
Question and response
Question
dig acc2243.wm-s.jp. NS
Answer
acc2243.wm-s.jp. 5 NS ns-1866.awsdns-41.co.uk.
acc2243.wm-s.jp. 5 NS ns-295.awsdns-36.com.
acc2243.wm-s.jp. 5 NS ns-805.awsdns-36.net.
acc2243.wm-s.jp. 5 NS ns-1319.awsdns-36.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0