Zest is a term reserved for the brightly rind of citrus fruits. Directly under the thin layer of zest is the white, cottony, bitter pith, which is to be avoided. Depending on the recipe, you might remove the zest in wide strips, slice it, dice it, or grate it, which is sometimes referred to as zesting. I use a Microplane grater to remove zest — it’s the quickest, most effective tool for the job — but you can use a zester or an old-fashioned box grater, if that’s what you’ve got. With zest, it’s the volatile oils that carry the flavor, so to make the most of them when you’re baking, grate the fruit over the recipe’s sugar, then use your fingertips to blend the sugar and zest together. Do this for about a minute, and the sugar will be moist and powerfully aromatic; best of all, all that fragrance will turn up in your dessert.