Sweet-and-Sour Fish (Stegte Fisk i Eddike)

Combine flour, 1/4 teaspoon salt and pepper in a wide shallow bowl or pie pan. Dip fish in the mixture to coat, shaking off the excess.

Heat oil in a large nonstick skillet over medium heat; add the fish and cook, in batches if necessary, carefully turning once, until opaque in the center and golden on the outside, 3 to 5 minutes per side. Transfer to a shallow glass dish large enough to fit the fillets in a single layer. Top with onion slices.

Combine vinegar, water, sugar, peppercorns, allspice berries, bay leaf and the remaining 1/4 teaspoon salt in a small saucepan and bring to a boil, stirring to dissolve the sugar. Immediately pour over the fish. Remove the bay leaf. Let marinate for at least 15 minutes at room temperature or cover, refrigerate and marinate for up to 3 days.

Remove the fish and onions from the marinade. Serve warm or chilled.