Hi

I want to make a Tart au Citron this evening and the recipe I have is for making the pasrty by hand, using room temperature butter. I get far better results when making shortcrust using a processor as these hands were not for pastry making made. I've googled a fair bit to get a recipe adapted for a processor and not only are they all different in terms of the order the ingredients are added, but they all seem to suggest cold butter rather than the room temp suggested in the by hand method.

Does anyone have a reliable processor recipe or suggestions as to whether the butter should be cold or not? I'm not confident with pastry and this is a special request birthday treat.