Apex domains cannot have CNAME records.
Question and response
Question
dig mycimbsecurities.com. NS
Answer
mycimbsecurities.com. 5 NS ns1.f5cloudservices.com.
mycimbsecurities.com. 5 NS ns2.f5cloudservices.com.
mycimbsecurities.com. 5 NS 3.140.118.214.
mycimbsecurities.com. 5 NS 52.14.213.208.
Authority
The response has no authority records.
Additional
ns1.f5cloudservices.com. 5 A 107.162.234.197
ns2.f5cloudservices.com. 5 A 107.162.176.221
ns1.f5cloudservices.com. 5 AAAA 2604:e180:1071:0:0:0:3:1
ns2.f5cloudservices.com. 5 AAAA 2604:e180:1071:0:0:ffff:6ba2:b0dd
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0