Apex domains cannot have CNAME records.
Question and response
Question
dig inf.bulletproof.net. NS
Answer
inf.bulletproof.net. 4 NS ns1.bulletproof.net.au.
inf.bulletproof.net. 4 NS ns0.bulletproof.net.au.
Authority
The response has no authority records.
Additional
ns0.bulletproof.net.au. 1 A 202.44.98.24
ns1.bulletproof.net.au. 1 A 64.71.152.56
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0