Apex domains cannot have CNAME records.
Question and response
Question
dig instra.net.au. NS
Answer
instra.net.au. 5 NS ns2.instradns.com.
instra.net.au. 5 NS ns3.instradns.com.
instra.net.au. 5 NS ns1.instradns.com.
Authority
The response has no authority records.
Additional
ns1.instradns.com. 5 A 75.2.6.34
ns2.instradns.com. 5 A 75.2.85.37
ns3.instradns.com. 5 A 99.83.188.20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0