Apex domains cannot have CNAME records.
Question and response
Question
dig extride.ad.jp. NS
Answer
extride.ad.jp. 5 NS ns2.extride.ad.jp.
extride.ad.jp. 5 NS ns1.extride.ad.jp.
Authority
The response has no authority records.
Additional
ns1.extride.ad.jp. 5 A 170.199.246.16
ns2.extride.ad.jp. 5 A 170.199.246.17
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0