Apex domains cannot have CNAME records.
Question and response
Question
dig spcloud.jp. NS
Answer
spcloud.jp. 5 NS ns-1517.awsdns-61.org.
spcloud.jp. 5 NS ns-1964.awsdns-53.co.uk.
spcloud.jp. 5 NS ns-217.awsdns-27.com.
spcloud.jp. 5 NS ns-815.awsdns-37.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0