Apex domains cannot have CNAME records.
Question and response
Question
dig tcif.telstra.com.au. NS
Answer
tcif.telstra.com.au. 4 NS adns01.bigpond.com.
tcif.telstra.com.au. 4 NS adns02.bigpond.com.
tcif.telstra.com.au. 4 NS adns03.bigpond.com.
tcif.telstra.com.au. 4 NS adns04.bigpond.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0