Apex domains cannot have CNAME records.
Question and response
Question
dig instra.com. NS
Answer
instra.com. 2 NS ns2.instra.net.au.
instra.com. 2 NS ns1.instra.net.au.
instra.com. 2 NS ns3.instra.net.au.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0