Apex domains cannot have CNAME records.
Question and response
Question
dig interspeed.co.nz. NS
Answer
interspeed.co.nz. 1 NS ns1.nameserverz.com.
interspeed.co.nz. 1 NS ns2.nameserverz.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0