Where does Passenger's error output go?

I can’t figure out where the error output from Passenger goes.
The apache error.log gets nothing but “file not found” errors.

Of particular interest are ruby startup errors (e.g. syntax or
can’t find gem.) These often flummox Passenger/Rack
to such an extent that all one gets is a "500 internal error"
or “Rack app couldn’t start” or “There is a problem
and we have been informed” page with no traceback or
syntax error information that I can find anywhere.

To answer my own question …

I got the answer from the DH staff. As a result, here is what I added to the Passenger page of the DH Wiki ( http://wiki.dreamhost.com/Passenger ) -

Output to STDERR for processes run through the Rack interface is directed to the master Apache error log file rather than the domain/subdomain specific log file. You do not have direct access to the master log file. This limitation can make debugging initialization errors (in particular syntax errors and gem resolution issues) tricky. Passenger will often produce an error output webpage including a stack traceback. However, in some cases it does not. If you have a persistent problem and Passenger is not producing sufficiently useful error output, you can try contacting the Dreamhost support staff and ask them to examine the master log file for you. Once a framework (such as RoR) is up and running, its error output is typically handled by the framework’s own error logging mechanism. For example, RoR records its error output in a file named “log/production.log”.