GTM Cache question

Hi All,

Regarding GTM, I have done following.

1. Configured Listener.
2. Enabled recursion in named configuration file.

So now, I can resolve DNS for public domains ex. .

Now, my question is..

If I try to resolve , GTM has NS entry somewhere and it directly contacts to same NS rather than root and TLDs. So I want to know where this NS information is stored? Caching is not enabled on GTM. Also, how to clear these entries?

Please suggest.