If you can't find fennel, this recipe transforms ordinary branch celery. I also sometimes use this as a sauce for pasta, adding some shaved Parmesan or ricotta salata to make it complete.
• 1 to 2 fennel bulbs or a head of celery (8 to 10 stalks), about 1 1/2 pounds
• 1 tablespoon extra-virgin olive oil
• 1 medium onion, peeled and finely chopped
• 3/4 cup water
• 1/4 teaspoon kosher salt
• 1/2 to 1 teaspoon fennel seed, crushed or coarsely chopped
• 1/4 cup black olives such as Calamata, Nicoise, or oil-cured Moroccan, pitted
• 1/2-inch strip lemon zest, finely slivered (optional)
• Freshly ground pepper to taste
With a vegetable peeler, remove any fibrous strings from the fennel or celery stalks. Slice the vegetables lengthwise into 1/4-inch slices. Cut the slices crosswise into inch-dice.
In a 10-inch skillet, over moderate heat, combine the olive oil and onion. Cover and cook, stirring occasionally, until the onion is translucent, about 5 minutes. Add 3/4 of the diced fennel or celery, the water, and salt. For fennel, add 1/2 teaspoon fennel seed; for celery, add 1 teaspoon of the seeds. Bring to a boil, reduce the heat, cover and simmer until the vegetables are tender and most of the liquid has evaporated, about 20 minutes. Stir in the reserved fennel or celery, the olives, and lemon zest. Season with salt and pepper to taste and serve at once.