Apex domains cannot have CNAME records.
Question and response
Question
dig kawamura-seitaiin.com. NS
Answer
kawamura-seitaiin.com. 5 NS ns-1510.awsdns-60.org.
kawamura-seitaiin.com. 5 NS ns-178.awsdns-22.com.
kawamura-seitaiin.com. 5 NS ns-150.awsdns-18.com.
kawamura-seitaiin.com. 5 NS ns-1404.awsdns-47.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0