Prepare the vegetables: Heat the olive oil in a pot over medium heat. Add the onions and cook until golden, 3 to 4 minutes. Add the fennel and cook until slightly soft, 2 to 3 minutes. Stir in the sugar and season with kosher salt and pepper. Add the vinegar, garlic and 1 cup water; bring to a boil, stirring, then reduce the heat to medium low and simmer until the onions are tender, about 25 minutes.
Meanwhile, prepare the fish: Finely chop the pine nuts by hand. Mix the nuts, lemon zest, parsley, and sea salt and pepper to taste on a cutting board. Pat the swordfish dry and brush with olive oil on both sides. Press the fish into the nut mixture, turning to coat.
Heat a large nonstick skillet over medium-high heat. Add 2 tablespoons olive oil and swirl to coat. When the oil shimmers, lay the fish in the pan and cook, undisturbed, until golden on the bottom, 4 to 5 minutes. Flip and cook until just golden on the other side, 3 to 4 more minutes. Using tongs, lay each swordfish steak on its side to sear the edges, 1 to 2 minutes. Reduce the heat to medium low. Turn the fish so the lighter side is down and cook until just firm to the touch, 6 to 8 more minutes. Transfer to a cutting board.
While the fish rests, finish the vegetables: Add the tomatoes, oregano, capers and brine to the onions and cook until the tomatoes soften, 5 to 8 minutes. Season with kosher salt and pepper.
Slice the fish and divide among plates. Spoon the vegetables and juices onto the plates. Drizzle with the lemon juice and olive oil.
Photograph by Con Poulos
Recipe courtesy of Food Network Magazine