Apex domains cannot have CNAME records.
Question and response
Question
dig salt.ac.za. NS
Answer
salt.ac.za. 5 NS froth.tlabs.ac.za.
salt.ac.za. 5 NS disa.tenet.ac.za.
salt.ac.za. 5 NS ns1.saao.ac.za.
salt.ac.za. 5 NS ns2.saao.ac.za.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0