Finely crush juniper, pepper and mustard seeds in a mortar. Add oil, lemon juice and 1 pinch of salt. Peel and chop the onion and mix with the spice paste
Wash the fish, pat dry and cut into 8 pieces. Place in a greased, wide ovenproof dish, scratch crosswise several times. Spread the spice paste over it. Cook in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for approx. 20 minutes
Spinach clean, wash. Peel and chop the garlic. Wash tomatoes and cut into slices. Steam everything in hot fat for about 5 minutes (cover frozen spinach and steam it with 100 ml water for about 15 minutes). Season to taste with salt and pepper. Arrange everything, garnish with lemon and parsley if necessary. Served with: rice