Apex domains cannot have CNAME records.
Question and response
Question
dig westcon.com.au. NS
Answer
westcon.com.au. 4 NS ns3.westcon.com.
westcon.com.au. 4 NS ns1.westcon.com.
westcon.com.au. 4 NS ns2.westcon.com.
westcon.com.au. 4 NS ns1.westcon.co.uk.
westcon.com.au. 4 NS ns4.westcon.com.
Authority
The response has no authority records.
Additional
ns1.westcon.co.uk. 4 A 216.150.156.4
ns1.westcon.com. 4 A 207.45.173.20
ns2.westcon.com. 4 A 216.150.156.51
ns3.westcon.com. 4 A 216.150.156.2
ns4.westcon.com. 4 A 207.45.173.10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0