Wash the fish, pat dry, place on a plate, sprinkle with lemon juice and season with salt and pepper. Wash 1 orange hot, rub dry. Peel off some of the peel with a peeler and cut into fine strips.
Halve the orange, squeeze 1 half. Peel 1 1/2 oranges so that the white skin is completely removed. Cut oranges crosswise into thin slices. Grease 2 small casseroles, line with orange slices.
Place 1 piece of fish on each. Dissolve the crustacean paste in approx. 100 ml hot water, mix with crème fraîche, 4-5 tbsp. orange juice, orange strips, except for a little for garnishing, and green pepper, season with salt and a little sugar.
Pour sauce over the fish. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 12-15 minutes, remove from oven and garnish with orange strips. Rice tastes good with it.