1. Zest has an intense flavor, which is why it is so valued by cooks. To make the most of this property, you should be sure to eliminate any of the fruit's white membrane, which has a bitter flavor. To zest fruit, use a vegetable peeler, paring knife, or "zester tool" (available at kitchen shops) to remove the outermost colored peel in long strips, as shown. Try to avoid digging into the fruit so deeply that you cut into the white underskin surrounding the fruit; cut off only the top, colored layer of the peel.
2. Lay each strip of peeling on a cutting board, outer side down. With a sharp knife, scrape away any white membrane adhering to the underside of the strip.
3. When you have cleaned the strips of all the membrane, use kitchen shears to finely snip the zest into small pieces, as shown.
4. Or use a French chef's knife to chop zest as finely as you like. Tightly covered, zest will keep in the refrigerator for several days.