Apex domains cannot have CNAME records.
Question and response
Question
dig vocus.net.nz. NS
Answer
vocus.net.nz. 5 NS ns-1906.awsdns-46.co.uk.
vocus.net.nz. 5 NS ns-1182.awsdns-19.org.
vocus.net.nz. 5 NS ns-44.awsdns-05.com.
vocus.net.nz. 5 NS ns-757.awsdns-30.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0