Apex domains cannot have CNAME records.
Question and response
Question
dig seeds.jp. NS
Answer
seeds.jp. 2 NS ns2.dns-server.jp.
seeds.jp. 2 NS ns1.dns-server.jp.
seeds.jp. 2 NS ns4.dns-server.jp.
seeds.jp. 2 NS ns3.dns-server.jp.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0