It is easiest to remove the zest from the lemon while it is still whole. You can rub it against the finest teeth of a grater (a Microplane works great) or remove the zest in strips with a vegetable peeler and then chop it finely. You can also substitute dried lemon peel for fresh zest. The dried product is already grated and is stronger than fresh so use about a third of the amount; approximately 1 teaspoon dried lemon zest equals the grated zest of 1 lemon. Dried zest can be found in the seasonings section of the supermarket.