Apex domains cannot have CNAME records.
Question and response
Question
dig cmweb.co.za. NS
Answer
cmweb.co.za. 5 NS petra.ns.1-grid.co.uk.
cmweb.co.za. 5 NS petra.ns.1-grid.com.
cmweb.co.za. 5 NS petra.ns.1-grid.co.za.
cmweb.co.za. 5 NS petra.ns.1-grid.net.
Authority
The response has no authority records.
Additional
petra.ns.1-grid.co.uk. 5 A 41.61.100.10
petra.ns.1-grid.co.za. 5 A 196.43.195.10
petra.ns.1-grid.com. 5 A 41.61.100.10
petra.ns.1-grid.net. 5 A 196.43.195.10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0