Apex domains cannot have CNAME records.
Question and response
Question
dig otherdns.com. NS
Answer
otherdns.com. 5 NS ns.dns1.co.za.
otherdns.com. 5 NS ns.dns2.co.za.
otherdns.com. 5 NS ns.otherdns.com.
otherdns.com. 5 NS ns.otherdns.net.
Authority
The response has no authority records.
Additional
ns.dns1.co.za. 5 A 169.1.2.99
ns.otherdns.com. 5 A 41.215.232.12
ns.otherdns.net. 5 A 149.28.240.39
ns.dns1.co.za. 5 AAAA 2406:da11:f5d:500:bbed:25d3:3efe:555a
ns.otherdns.com. 5 AAAA 2001:19f0:7400:1a54:5400:3ff:fee2:36a5
ns.otherdns.net. 5 AAAA 2001:19f0:6402:4eb:5400:1ff:fea2:bf1f
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0