Apex domains cannot have CNAME records.
Question and response
Question
dig aussiebroadband.com.au. NS
Answer
aussiebroadband.com.au. 5 NS thomas.ns.cloudflare.com.
aussiebroadband.com.au. 5 NS val.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0