Apex domains cannot have CNAME records.
Question and response
Question
dig backyard-tokyo.com. NS
Answer
backyard-tokyo.com. 5 NS ns-702.awsdns-23.net.
backyard-tokyo.com. 5 NS ns-944.awsdns-54.net.
backyard-tokyo.com. 5 NS ns-1613.awsdns-09.co.uk.
backyard-tokyo.com. 5 NS ns-591.awsdns-09.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0