Preheat the oven to 250 degrees F and set a wire rack on a baking sheet. Season the swordfish on both sides with salt and pepper. Wrap each steak with 1 or 2 slices of prosciutto, until just covered, without overlapping too much. Set aside.
Using a paring knife, peel the oranges, removing all the white pith. Working over a mixing bowl to catch the juice, cut between the membranes to release the segments; add to the bowl. Add the raisins to the bowl so they plump while preparing the rest of the dish. Trim the stalks from the fennel bulbs, reserving the fronds for garnish; remove the tough outer leaves. Cut each bulb in half lengthwise, trim the base and cut out the core. Slice the fennel into strips as thin as possible. Put the fennel slices in the bowl and add the olives, anchovies, vinegar, 1/4 cup olive oil, the basil and fennel seeds. Season with salt and pepper and toss gently to mix.
Heat 3 tablespoons olive oil in a large nonstick skillet over medium-high heat. When shimmering, carefully add 4 of the swordfish steaks and cook until the prosciutto is browned and crisp and the fish is just cooked through, about 3 minutes per side. Transfer to the baking sheet and keep warm in the oven. Wipe out the skillet, add the remaining 3 tablespoons oil and repeat with the remaining fish.
Serve the fish over the fennel salad. Garnish with the arugula, cherry tomatoes and reserved fennel fronds.
Photograph by Yunhee Kim