You mentioned RoR and Zend Frameworks, but I can suggest to take a look at seaside.

This is a smalltalk web framework (obj-c takes a lot of idea from smalltalk, so this can be a good match for a cocoa developer).

One of the sweetest feature of seaside is the availability of an integrated debugger in the browser environment that you can use during development:
small screencast.

best regards
nibble