Apex domains cannot have CNAME records.
Question and response
Question
dig vonex.com.au. NS
Answer
vonex.com.au. 5 NS ns-962.awsdns-56.net.
vonex.com.au. 5 NS ns-1863.awsdns-40.co.uk.
vonex.com.au. 5 NS ns-150.awsdns-18.com.
vonex.com.au. 5 NS ns-1336.awsdns-39.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0