$ORIGIN example.com.
$TTL 3600
example.com.  IN  SOA   ns1.example.com. admin.example.com. ( 2020091025 7200 3600 1209600 3600 )

example.com.  IN  NS    ns1
example.com.  IN  NS    ns2

ns1           IN  A     192.0.2.2
ns2           IN  A     192.0.2.3

@         IN  A     192.0.2.1