Apex domains cannot have CNAME records.
Question and response
Question
dig vocus.co.nz. NS
Answer
vocus.co.nz. 5 NS ns-910.awsdns-49.net.
vocus.co.nz. 5 NS ns-1897.awsdns-45.co.uk.
vocus.co.nz. 5 NS ns-506.awsdns-63.com.
vocus.co.nz. 5 NS ns-1066.awsdns-05.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0