Tomatoes Stuffed With Blackfish

1 ¼ pounds fresh, thick blackfish fillets
6 medium-to-large ripe tomatoes (about 2 1/2 pounds)
1 small cucumber (about 6 ounces), peeled, seeded, and cut into 1/4-inch dice (1 cup)
4 radishes, cleaned and cut into 1/4-inch dice (1/2 cup)
4 scallions, cleaned and minced (1/2 cup)
2 cloves garlic, peeled and finely chopped (1 teaspoon)
½ cup loose coriander leaves

Nutritional Information
- Nutritional analysis per serving (6 servings)
  251 calories; 14 grams fat; 2 grams saturated fat; 0 grams trans fat; 3 grams monounsaturated fat; 7 grams polyunsaturated fat; 10 grams carbohydrates; 3 grams dietary fiber; 6 grams sugars; 19 grams protein; 38 milligrams cholesterol; 340 milligrams sodium

Six servings

Arrange the fish on a plate and place in a steamer. Place on the stove and bring to a boil. Steam for six to eight minutes, until the fish just flakes but is still quite moist and barely cooked. Let cool to room temperature and then flake, separating the fillets into one-inch pieces. You should have approximately two cups.
Cut off the top third of each tomato and press each base lightly to extract a little of the juice and seeds. Using a measuring tablespoon (because it has sharp edges), remove the inside of each tomato base and top. (This flesh, and the ”lids,” will amount to approximately one and a quarter pounds and can be used in the bean recipe instead of the plum tomatoes.)
To make the vinaigrette, combine the mustard, red-wine vinegar, Worcestershire sauce, oil, salt and pepper in a bowl and mix well. Add the cucumber, radish, scallion and garlic to the vinaigrette and stir to combine. Gently fold in the fish and coriander so as not to break the fish too much.
Arrange the tomato receptacles in a gratin dish and stuff lightly with the fish mixture, heaping the filling. Cover with plastic wrap and refrigerate until time for the picnic. (The tomatoes can be stuffed a few hours ahead and refrigerated, but should be eaten at room temperature for best flavor.)

30 minutes