Classic Passover Baked Whitefish With Dill And Tomato-Cucumber Relish

• vegetable oil
• 2 pound whitefish, cut into 2 fillets, fatty portions trimmed along center and flap edges
• 3 cup fresh dill, coarsely chopped
• 1 medium onion, coarsely chopped
• 1 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 6 tablespoon white vinegar
• 4 cup cucumber, peeled, seeded, and diced
• 2 pound plum tomatoes, seeded and chopped
• 1/2 cup fresh dill, chopped
• 1/4 cup white vinegar
• 4 teaspoon kosher salt
• freshly ground black pepper
• fresh dill, for garnish

1. Line a heavy baking sheet with foil, and brush with oil. Arrange the fish skin side down on the foil.
2. Put the dill and onion in the food processor and pulse until finely chopped.
3. Sprinkle each fillet with half the salt and pepper. Press the dill mixture firmly over the fillets. Pour the vinegar over the top. Cover and chill overnight.
4. Preheat the oven to 375 degrees.
5. Uncover the fish and bake in the center of the oven until just cooked through, about 25 minutes. Let stand at room temperature for 30 minutes. Cover and chill for at least 2 hours before serving.
6. Combine the cucumber, plum tomatoes, dill, vinegar, and salt in a medium bowl. Let stand for 3 hours, stirring occasionally. Season with pepper.
7. Scrape most the dill off the fish. Cut the fish crosswise into 12 portions. Slide a spatula under the fish to remove the skin. Arrange fish on plates, and spoon over the relish. Garnish with extra dill.