Apex domains cannot have CNAME records.
Question and response
Question
dig knossos.net.nz. NS
Answer
knossos.net.nz. 4 NS ns2.liverton.net.nz.
knossos.net.nz. 4 NS ns3.liverton.net.nz.
knossos.net.nz. 4 NS ns1.liverton.net.nz.
Authority
The response has no authority records.
Additional
ns1.liverton.net.nz. 4 A 54.151.99.84
ns2.liverton.net.nz. 4 A 202.160.60.20
ns2.liverton.net.nz. 4 A 202.160.60.22
ns3.liverton.net.nz. 4 A 13.239.94.244
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0