What should I do if I draw a blank during an interview?

Answer honestly that you don’t know, why you may not be in a position to have that knowledge, and what you can/will do to bridge the gap.

Pause briefly. Take a breath. Consider for a moment. It will come back to you and the other person will not notice. Look down at your notes if the eye contact is too awkward. Last resort, tell them you lost your train of thought. It happens to everyone. They will set you back on track and not even remember the incident.

Ask for examples of what they are looking for.

Be honest. The worst thing in this scenario is to make up an answer that the interviewer can see through. You will be immediately discredited.

explain how you'd figure it out or go about finding an answer in the context of the workplace

You will always be able to find something to say. Keep a notepad handy jot down quick idea words related to question. As you think say something like "That is an interesting question/idea and I haven't really thought much about it, but I would have to say [blah, blah, blah]...and I will certainly think about the issue in the future. Thank you for the question!

Unless it’s in the middle of a sentence the easiest thing is to repeat the question back as you collect your thoughts. For example if the question is “what do you think is your best quality as an employee?” You can respond “I believe my best quality as an employee is...” this will buy you a few seconds to prepare mentally.