1. Pat the fillets thoroughly dry with kitchen paper and season lightly with salt and pepper. In a large pan, add the olive oil and sauté the onion until golden brown. Add the garlic and continue sautéing for 1 minute.
2. Add the tomato paste and stir it around the bottom of the pan to release its aromas. Add the cherry tomatoes, sugar, wine, and let the alcohol evaporate slightly. Add the capers, olives, oregano, the remaining salt and pepper. Pour in the water and place the fish fillets on top.
3. Cover the pan and simmer gently for 10-15 minutes, or until the fish is cooked. Occasionally, shake the pan and spoon some sauce over the fish. Just before the end, sprinkle with the parsley. Serve while hot!
