In my opinion, the lemon is the most underutilized of all seasonings. Its use should not be limited to just water, tea, and lemonade. The lemon originated in Northern India and was carried to Europe by the Arab Invaders in Spain and by returning Crusaders. Both its zest, the thin outer colored skin, and its juice are used. However, beware, the white pith layer below the zest is bitter and should not used. Lemon zest has a more intense flavor and aroma than juice, while the juice is more acid. Zest is often called for in baking where the acid and extra liquid would interfere with the result. The zest is also used with herbs, especially rosemary, in an oil-based marinade or basting sauce for meat. Lemon juice is more likely to be used in a seafood marinade, for example ceviche, or squeezed on food after cooking. Try fresh squeezed lemon juice on grilled meat or a baked potato. The best way to produce lemon zest is with a micro plane (top of picture). It results in a finer grate than a vegetable grater, producing more flavor. One medium-sized lemon has approximately 1 tablespoon of zest and 2 to 3 tablespoons juice.
Also pictured (to the left) are two stalks of lemon grass. Lemon grass has a pleasant lemon flavor and is a common ingredient in Southeast Asian cooking, especially Vietnamese. Fresh lemon grass is generally available only in Oriental markets.
Listed below are some approximate equivalents for use in a pinch.
1 measure dried zest = 1 measure fresh zest
1 teaspoon zest = 2 tablespoons juice
2 stalks lemon grass = 1 tablespoon zest
Preserved lemons are common in North African recipes, but not so in other cuisines. They are produced by packing cut lemons in salt and covering them with lemon juice. For use, the pulp is scraped off and only the rind is used. They provide a slightly bitter lemon flavor with a fermented note. I do not go into more detail here because they are not a commonly called for ingredient