Apex domains cannot have CNAME records.
Question and response
Question
dig ipng.com.au. NS
Answer
ipng.com.au. 4 NS per.dns.ipng.net.au.
ipng.com.au. 4 NS wtl.dns.ipng.net.au.
ipng.com.au. 4 NS sy4.dns.ipng.net.au.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0