Apex domains cannot have CNAME records.
Question and response
Question
dig hostingplatform.net.au. NS
Answer
hostingplatform.net.au. 3 NS ns2.corp.ventraip.net.au.
hostingplatform.net.au. 3 NS ns3.corp.ventraip.net.au.
hostingplatform.net.au. 3 NS ns1.corp.ventraip.net.au.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0