Apex domains cannot have CNAME records.
Question and response
Question
dig s.d-53.net. NS
Answer
s.d-53.net. 3 NS ns.iij-dns.jp.
s.d-53.net. 3 NS ns.iij-dns.net.
s.d-53.net. 3 NS ns.iij-dns.biz.
Authority
The response has no authority records.
Additional
ns.iij-dns.jp. 2 A 162.159.26.71
ns.iij-dns.jp. 2 A 162.159.27.34
ns.iij-dns.biz. 2 A 202.32.219.52
ns.iij-dns.jp. 2 AAAA 2400:cb00:2049:1:0:0:a29f:1a47
ns.iij-dns.jp. 2 AAAA 2400:cb00:2049:1:0:0:a29f:1b22
ns.iij-dns.biz. 2 AAAA 2001:240:bb81:0:0:0:28:52
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0