The Italian title calls for John Dory as the fish, and by all means use it if you can find it, but otherwise sea bass will be just as delicious.
6 tablespoons extra-virgin olive oil
1 medium onion, chopped
1 pound red potatoes, peeled and cut in 1/2-inch cubes
2 tablespoons tomato paste
2 stalks celery , with leaves, chopped
2 bay leaves, preferably fresh
1 teaspoon kosher salt
12 cups cold water
1 pound skinless sea-bass fillet, cut in 1 1/2-inch cubes
2 medium ripe tomatoes, cut in 1-inch cubes
1½ pounds fresh Taccozze
You will need a wide, heavy-bottomed sauté pan or saucepan, 13-inch diameter, with a cover.
To make the sauce: Pour the olive oil into the big pan, set it over medium heat, and scatter in the onion. Cook, stirring, for 3 or 4 minutes, until it begins to soften. Toss in the potato cubes, stir with the onions, and spread them out in the pan; cook for 5 minutes or so, tumbling them over occasionally, until they start to caramelize and stick to the pan bottom. Clear a space in the pan, and drop in the tomato paste; let it caramelize and toast in the hot spot for a minute, then stir together with the onion and potatoes.
Drop in the celery and bay leaves, sprinkle on the salt, stir, and get everything sizzling, then pour in the cold water. Stir up the vegetables, cover the pot, and bring the water to a boil over high heat. Adjust the heat to keep it bubbling nicely, and cook for 30 to 40 minutes, until the potatoes start to fall apart and thicken the sauce.
Drop in the cubes of fish and tomatoes, stir to distribute them, and heat the sauce back to an active simmer. Cook, uncovered, for 15 minutes or so, until the sea bass is cooked through and the tomatoes have softened and dissolved into the sauce.
Before cooking the taccozze—right in the sauce itself—I shake the diamond shapes by handfuls in a colander or strainer, removing excess flour. Then I drop all of the pasta at once into the simmering sauce. Stir and lift the taccozze with tongs, separating the flat pieces if they are stuck together. Cover the pan, and bring sauce to a boil over high heat; cook the taccozze for about 4 minutes, stirring frequently, until al dente. Serve immediately in warm soup bowls.