One of the easiest ways to infuse a citrus flavor into a baked good of some kind is to add lemon, lime or orange zest to it. Zest is not the same thing as the peel, or rind, of a lemon, although it is a part of the peel. The zest is the colorful outer layer of the citrus peel. The soft, white part of the peel just underneath the zest is the pith. The reason that the zest is so desireable is that it contains lots of essential oils that make for a strong, pleasant flavor. The pith has a bitter flavor, with very little citrus taste when eaten on its own.
The pith can actually give your baked good a bitter or slightly unpleasant taste if you incorporate it into a recipe (there are some recipes that call for using a whole fruit, but those usually compensate with extra sugar), so it is important to remove only the zest from the citrus rind when you are using it. The zest can be removed very carefully with a sharp pairing knife, but the easiest and best way to remove the zest is with a microplane. Wash your fruit very, very well before zesting it – or try to buy organic/unwaxed fruit – so that you don’t incorporate any unwanted elements into your zesting. A zested lemon can be wrapped in plastic wrap to keep it from drying out, and stored at room temperature for several days.
Zest can be added to cookies, cakes and all kinds of other recipes. Unlike lemon or orange juice, it doesn’t throw off the chemistry of the recipe (either by adding more acidity or more liquid), so you can feel confident adding a teaspoon or a tablespoon of zest to just about any recipe you want to make a little brighter. Adding zest to a recipe that already has citrus juice is a great way to enhance the flavor that is already there, as well.