Mix yoghurt and 3 tablespoons of lemon juice. Season with sugar, salt and pepper. Wash the dill and shake dry. Pluck flags from the stalks and chop finely. Wash apple, grate dry and grate.
Mix apple, horseradish, dill, breadcrumbs and egg. Season with salt, pepper and 2 tablespoons lemon juice. Cook rice in boiling salted water according to package instructions. Meanwhile wash the fish, dab dry and cut into 4 slices.
Heat butter in a frying pan. Sauté the fish on the skin side for about 1 minute. Place slices on a baking tray and spread the horseradish mixture unevenly. Pour on the stock. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 10 minutes.
In the meantime, wash the lamb's lettuce thoroughly. Halve the pomegranate and remove the seeds. Mix pomegranate seeds and lamb's lettuce. Arrange fish and salad on plates. Drizzle with yoghurt sauce. Add rice.