Many instant farinata recipes advise to let the batter rest for a half hour in the fridge prior to cooking. I have tried both letting it rest and cooking it directly and saw no noticeable difference in the results. The batter can be stored in the fridge for a few hours, though, and farinata tastes best when it's freshly made. You can make the batter in advance and keep it refrigerated to just cook it when it's time to serve the farinata to your guests.