Apex domains cannot have CNAME records.
Question and response
Question
dig bsrv.jp. NS
Answer
bsrv.jp. 5 NS ns-1196.awsdns-21.org.
bsrv.jp. 5 NS ns-260.awsdns-32.com.
bsrv.jp. 5 NS ns-1018.awsdns-63.net.
bsrv.jp. 5 NS ns-1602.awsdns-08.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0