Use your discussion of the event to refer to the question-and-answer portion:
At the ZEE Jaipur Literature Festival in January 2018, I had the opportunity to ask Tom Stoppard a question about his play The Real Thing during the question-and-answer portion of his panel discussion with Sanjna Kapoor (Kapoor and Stoppard).
To create a works-cited-list entry for the event, give the session participants in the “Author” slot, the title or description of the session in the “Title of source” slot, the conference name as the title of the container, and the date and location of the session:
Kapoor, Sanjna, . . .
Published 23 May 2019