Apex domains cannot have CNAME records.
Question and response
Question
dig infra.tppw.com.au. NS
Answer
infra.tppw.com.au. 5 NS ns-283.awsdns-35.com.
infra.tppw.com.au. 5 NS ns-558.awsdns-05.net.
infra.tppw.com.au. 5 NS ns-1368.awsdns-43.org.
infra.tppw.com.au. 5 NS ns-1654.awsdns-14.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0