“What question do you want me to ask you?”
If I were asked this question in a real life interview situation, it might throw me off a bit. I’d have prepared with answers to questions that I thought the potential employer would have asked me as it applied to how I could help them achieve their goals, but I don’t know that I would have prepared to provide them with a question to help them do so.
The way to backward engineer the “answer” to this question is to think about what things you could tell them about yourself that could really make you stand out as a candidate–what are you most proud of? Then form a question that would merit that response.