Is the Mikrotik DNS cache secured against this?
it was discussed already. yes, it is secure, because MikroTik DNS server is not resursive
I think Mikrotik DNS server/cache is recursive though. Oh, wait. It depends on the parent DNS server it uses.
I did a test on my Mikrotik boxes and they all got a clean bill of health. They must use random source ports for lookups and they appear to be doing that. Or likely there parent DNS servers are.
Directions to test a DNS server are here.
https://www.dns-oarc.net/oarc/services/porttest
Matt