The bright flavor that makes citrus fruits a cherished kitchen staple is only partly found in their flesh. Much of it comes instead from volatile, intensely flavored oils found in the peel of oranges, lemons, limes and other citrus fruits. This peel is often a crucial ingredient in recipes, where it's referred to as the fruit's "zest." Specialized zesting tools are available, but you don't need one to make zest at home.
With a Zester
There's a tool designed specifically for almost every imaginable kitchen task, and that includes zesting. Professional-style zesting tools are available at good kitchenware outlets, both brick-and-mortar and online. Their metal "business end" has four or five circular cutting edges, which create long, beautiful, uniform strips of zest. Just position the tool at the top of your orange, lime or lemon, and apply gentle pressure as you draw the tool around the fruit to the bottom. Turn the fruit and repeat, until you've either bared it completely or gathered as much zest as you need. Use the strips as is, for decorative purposes or chopped into finer pieces as needed.
With a Grater
Unless you work with citrus regularly -- or are a passionate collector of kitchen gadgetry -- you're unlikely to have a zester in your kitchen drawer. You probably have at least one grater, though, which makes a perfectly fine zester. If you're using a traditional-style box or flat grater, try the fine side first. If that tends to pulp the peel rather than bringing it off in useful pieces, switch to the grater's coarse side. Rotate the fruit as you go, until the colorful zest is removed and only the bitter white pith remains. Modern blade-style graters, with razor-sharp cutting edges, zest more efficiently than traditional graters. Some manufacturers specifically market extra-fine graters as zesting tools.
With a Peeler or Paring Knife
Zesting a lemon, lime or orange with a knife or peeler is a bit more work, but provides the maximum in versatility. Cut away broad strips of peel from the fruit with shallow strokes, leaving behind as much of the bitter white pith as possible. Lay the large strips of peel on a cutting board, and shave away any excess pith by sliding a paring knife horizontally along the cut inner surface of the peel. Cut the remaining zest as you need it for a recipe a dish. Julienne it as a garnish, for example, or coarsely chop it for use in a muffin or coffee cake.
A Few Pointers
Prepared zest can go into many recipes directly, as soon as you've sliced, chopped or minced it to the correct size. In marinades or many baked goods, there's nothing more to do. However, if you're using larger pieces -- or if the zest is a major ingredient -- it's sometimes better to "blanch" it to quell any bitterness. Just put your zest in a heatproof cup or dish and pour in boiling water. After 15 to 20 seconds, transfer the zest to a bowl of ice water to stop the cooking, then drain and dry it. The blanched zest can be dried, frozen or candied for later use.