Apex domains cannot have CNAME records.
Question and response
Question
dig tnbt.jp. NS
Answer
tnbt.jp. 5 NS ns-1982.awsdns-55.co.uk.
tnbt.jp. 5 NS ns-1149.awsdns-15.org.
tnbt.jp. 5 NS ns-291.awsdns-36.com.
tnbt.jp. 5 NS ns-619.awsdns-13.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0