Lemons actually is the correct ingredient to index when a recipe calls for lemon zest. The reason for that is because you need lemons in order to get lemon zest. The same goes for zest (or freshly squeezed juice) of any other citrus fruit. For Personal Recipes, I would recommend making yourself a note in the "Notes" field if you would like to differentiate between fresh juice or fresh zest (or both) when indexing lemons. Hope that helps!