CNAME Flattening

Hi,

F5 GTM's are our domain (let us say example.com) authorized DNS servers. Our website is accessible on  example.com and www.example.com. We are migrating to the cloud and the DNS queries will still hit the GTM's and we need to redirect to the Cloud front door (CNAME Record).

The existing set up is with the 2 WIP's(www.example.com and example.com) on the GTM points to the pool. To migrate, we have created the CNAME records in the zonerunner , the challenge is we cant create the CNAME record for the root zone (example.com) as there will be NS records etc. We have created CNAME based WIDEIP for example.com with the CNAM based pool (Cloud front door).  When i access example.com , we get the error on the browser saying "DNS prod finished nxdomain error".  When i dig specifically with CNAME on google DNS, Dig interface I can see the CNAME record.

Tried with few irules, however we are getting errors.

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when DNS_REQUEST {
set queried_name [DNS::question name]
set Cloud_FD "abc.xyz"
    if { [string tolower $queried_domain] eq "example.com" } {
        set cname_record "${queried_name}. 300 IN CNAME ${Cloud_FD}."
        set new_rr [DNS:rr ${cname_record}]
        DNS::answer clear
        DNS::answer insert $new_rr
        DNS::return
    }
}

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