Apex domains cannot have CNAME records.
Question and response
Question
dig sitehost.nz. NS
Answer
sitehost.nz. 5 NS ns3.sitehost.co.nz.
sitehost.nz. 5 NS ns2.sitehost.co.nz.
sitehost.nz. 5 NS ns1.sitehost.co.nz.
sitehost.nz. 5 NS ns4.sitehost.co.nz.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0