I cannot emphasize this enough. Coding is the EASY part of writing software. You can teach someone to code in a couple of months. Interviews that focus on someone's ability to code are just dumb.

What you need to do is see how well they can design before writing software. What is their process for designing the software they make? Can they architect it correctly? How do they capture user's mental models? How do they deal with the many "tops" that software has?