Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper.
Add a drizzle of EVOO to a small skillet and toast the panko and bread crumbs until golden. Remove and cool.
In a food processor, pulse-chop the fish into very fine pieces, then transfer to a bowl. Season with salt and pepper.
On a cutting board, chop the parsley, then add the lemon zest and garlic and continue chopping these together to form a gremolata. Add the gremolata to the fish, along with the egg, onion, tomato, 3 tablespoons EVOO, and cooled bread crumbs. Mix to combine.
Use a 2-ounce scoop or spoon out about 2 rounded tablespoons of the swordfish mixture and roll one test ball (about the size of an oversize walnut). Roast for 10 to 12 minutes to taste for seasoning. Adjust the seasonings, if necessary, then roll the remaining balls and roast until opaque, cooked through, and lightly golden at the edges, 10 to 12 minutes.
Serve with Arugula Pistou on the side.
Add the lemon juice, arugula, olive oil, and garlic to a high powered blender and blend until smooth. Adjust seasoning with salt and pepper.