Apex domains cannot have CNAME records.
Question and response
Question
dig okweb3.jp. NS
Answer
okweb3.jp. 4 NS ns-1021.awsdns-63.net.
okweb3.jp. 4 NS ns-1827.awsdns-36.co.uk.
okweb3.jp. 4 NS ns-186.awsdns-23.com.
okweb3.jp. 4 NS ns-1173.awsdns-18.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0