Hello have you followed this?:
Pay attention to this:
*********
If you want the BIG-IPDNS to respond to both A and CNAME record type requests, you must configure two wide IPs. One wide IP of type A with a CNAME pool type, and a second wide IP of type CNAME with a CNAME pool type. At a minimum, an A record type wide IP should be configured with a CNAME pool.
***********
https://techdocs.f5.com/en-us/bigip-16-0-0/big-ip-dns-implementations/redirecting-dns-queries-using-a-cname-pool.html
Please mind that the f5 wide ip will use a CNAME pool that normally are pools with other WIDE IP objects that have real nomal A records, so the order is WideIP A record > CHAME record pool > WIDEIP A record > A record Pool. If the CNAME that dns is being redirected is not another Wide IP on the F5 device with a normal A record pool that can give real DNS resolution to the client LDNS then read:
Pay attention to this:
*********
Note: If you want BIG-IP DNS to use a CNAME record that does not exist on the device, check the Static Target box and type in CNAME (such as test.com) for Wide IP .
*********
https://support.f5.com/csp/article/K02935080