ns4.small-dns.com has no CNAME records.
Question and response
Question
dig ns4.small-dns.com. NS
Answer
The response has no answer records.
Authority
small-dns.com. 1334 SOA dns1.small-dns.com. root.small-dns.com. 1704202106 7200 300 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0