Diminutive (about the size of a large walnut), more acidic, and more yellow than common Persian limes, Key limes should have smooth, bright skin that is tight but not hard, with no puckering; small brown patches are OK. Like all citrus, choose limes that are heavy for their size; because they’re small, Key limes often are sold in mesh bags. Store, refrigerated in plastic, for a week.
The star ingredient in its namesake pie, Key limes shine in desserts but also lend a distinctive zip to savory dishes. Substitute lime juice for half of the lemon juice in your favorite lemon cookie or bar recipe. Add a squeeze to melon or fruit salads, especially those with tropical mangoes, pineapple, and papaya, to enhance flavors (this works in fruit cobblers and pies, too). For a refreshing breakfast, stir Key lime juice or zest into vanilla yogurt with frozen blueberries and serve over granola.
Key lime juice makes a wonderful dressing or marinade ingredient for blanched vegetables or seafood. Mix two parts lime juice with 1 part orange juice, minced jalapeño, and minced onion; drizzle over cooked squash, asparagus, cauliflower, or broccoli. Or, to make a simple ceviche, soak scallops in the above mixture for 24 hours, stirring once or twice, until opaque; drain and mix with finely chopped bell pepper, cilantro, and avocado.
Mix Key lime zest with butter, minced garlic, and minced parsley; roll into a log, wrap in waxed paper, and refrigerate. Use to flavor cooked fish, poultry, or pasta.
Add the juice of one Key lime to a pot of chicken soup to perk up flavor and add immune-boosting vitamin C. Bursting with this powerful nutrient, limes helped prevent scurvy among 18th-century British sailors, prompting the nickname “limey.”