Apex domains cannot have CNAME records.
Question and response
Question
dig eco-serv.jp. NS
Answer
eco-serv.jp. 5 NS ns-323.awsdns-40.com.
eco-serv.jp. 5 NS ns-1846.awsdns-38.co.uk.
eco-serv.jp. 5 NS ns-1339.awsdns-39.org.
eco-serv.jp. 5 NS ns-737.awsdns-28.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0