How to build whitelist dns

How to build whitelist dns

I need to build a whitelist dns.
I am half way there ... I am using authoritative powerdns and entering
only the whitelisted domains in the "records" database table.
I have two problems:
a) I can whitelist specific subdomains, but I can't figure out the format
for whitelisting a complete domain. I can whitelist "images.google.com"
but "google.com" is still blocked. I tried entering "*.google.com" but
that didn't work.
b) Requests for domains which are not on the whitelist come back as "page
cannot be displayed" ... I'd like to throw up a block page so how would I
redirect or default all unresolved requests to a specific page on the same
server, or even a different server? The nxdomain script might do it but I
can't find documentation anywhere on how to implement.
Thanks in advance.