A lot of our tasters said this dish reminded them of why they like rustic Italian food: We pretty much left the fennel alone here, just browning it in olive oil (don't be afraid of the high heat at this stage) and then covering it and letting it bubble in water and its own juices. It cooks down sweet and tender, and then gets one final boost of bright flavors from lemon and olive. We think it's great served at room temperature, about 30 minutes after cooking. This side dish is delicious warm or at room temperature, not hot.
Trim the tops and bottoms from the fennel bulbs, reserving a handful of the fronds. Quarter the bulbs. Set each quarter on its side and slice off most of the core. Cut the quarters into wedges about 1-inch thick (don't worry if some pieces fall off the wedge-use those too).
In a large skillet with a tight-fitting lid, heat the olive oil over medium-high heat until almost smoking. Add the fennel and cook, without stirring, until golden brown on the bottom, about 5 minutes. Stir and let some more pieces brown for a minute or two.
Stir in 1/2 cup water, scraping the bottom of the pan. Season with salt and pepper. Lower the heat to medium and cover the pan. Simmer, shaking the pan and adding more liquid occasionally if the pan is dry, until the fennel is very tender, 12 to 15 minutes.
Meanwhile, chop the reserved fennel fronds and mix them with the lemon zest.
When the fennel is tender, stir in the lemon juice and cook for 1 minute. Stir in the olives, remove from the heat and let stand for about 1 minute to warm the olives. Transfer the fennel to a platter. Sprinkle the fennel frond mixture over the top, drizzle with additional olive oil and serve.