For the sauce, peel onion and garlic and dice finely. Wash the thyme, shake dry and remove the leaves. Heat 1 tablespoon of oil in a saucepan. Sauté onion and garlic in it. Add canned tomatoes, bring to the boil. Season with salt, pepper, 1 tsp. sugar and thyme. Simmer for about 10 minutes, then puree finely.
For the ratatouille, clean and wash the eggplant and courgette. Wash the tomatoes. Cut vegetables into thin slices. Preheat oven (electric cooker: 160 °C/circulating air: 140 °C/gas: see manufacturer). Pour sauce into a flat casserole dish. Spread the vegetables on it like roof tiles. Season with salt and pepper. Cover the dish with baking paper. Bake in a hot oven on the grill for about 30 minutes.
For the potatoes, line a baking tray with baking paper. Peel and wash the potatoes and slice them into fine sticks. Mix with 2 tablespoons of oil and salt. Spread flat on the baking tray. Turn up the oven temperature (electric cooker: 180 °C/circulating air: 160 °C/gas: see manufacturer). Add potatoes to the vegetables in the oven and continue baking for about 30 minutes.
Dab fillets dry, season with salt and pepper. Heat 2 tablespoons of oil in a large frying pan. Brown the meat all around, remove. Cook for the last 15 minutes on the grill in the oven. Wash parsley and tarragon, shake dry, chop finely. Roll the meat in the herbs and cut into slices. Arrange everything.