1. Pulse the fish cubes in a food processor until finely chopped. Transfer to a large bowl and add the garlic and red pepper flakes; season with salt and pepper and mix thoroughly. Score the mixture into 4 equal portions and form them into patties of even thickness.
2. Grate the zest from the lemon. In a shallow bowl, mix together ? cup of the parsley, the lemon zest, and panko. Press the burgers in the seasoned crumbs to coat them completely.
3. Heat a thin layer of the oil in a large skillet over medium to medium-high heat. Cook tuna burgers, turning once, 8 minutes, or until golden brown and slightly pink at the center. Cook swordfish burgers, turning once, 10 to 12 minutes, or until cooked through. Squeeze the juice of ? lemon over the patties just before removing them from the skillet.
4. In a medium bowl, combine the remaining ? cup parsley, the tomatoes, capers, red onion, and basil. Drizzle with extra virgin olive oil and season with salt and pepper.
5. Place the burgers on the roll bottoms and top with tomato relish. Set the roll tops in place.
Per serving: 620 calories, 61 grams protein, 50 grams carbohydrates, 5 grams sugar, 18 grams fat, 83 milligrams cholesterol, 580 milligrams sodium, 4 grams dietary fiber