Apex domains cannot have CNAME records.
Question and response
Question
dig sharenet.co.za. NS
Answer
sharenet.co.za. 1 NS ns2.r4ns.net.
sharenet.co.za. 1 NS ns1.r4ns.com.
sharenet.co.za. 1 NS ns2.r4ns.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0