Apex domains cannot have CNAME records.
Question and response
Question
dig rest.com.au. NS
Answer
rest.com.au. 5 NS ns-1767.awsdns-28.co.uk.
rest.com.au. 5 NS ns-819.awsdns-38.net.
rest.com.au. 5 NS ns-479.awsdns-59.com.
rest.com.au. 5 NS ns-1532.awsdns-63.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0