Rinse the thawed or fresh fish fillets and dry them with paper towels. Rub on both sides with the lemon juice. Mix the salt into the flour and keep it ready. Arrange the washed and sorted Frisée leaves on the serving plates. Mix the ingredients for the dressing together
Wash the tomatoes, remove the stems, peel them, quarter them lengthways, remove the green stems and the grains. Halve the quarters lengthways and crossways. Cap the garlic cloves at both ends, peel and squeeze with a garlic press. Wash the small, green chillies and cut them crosswise into thin slices. Leave the grains and discard the stems.
Stew the above ingredients with 2 tablespoons of olive oil in a saucepan for 2 minutes, then deglaze with the tomato juice. Add all ingredients from the herb mix to salt and simmer for 3 minutes. Add the other additions except for the pecorino and stir until homogeneous.
Prepare the serving plates with the washed frisée leaves. Pluck the leaves from the fresh celery and chop them roughly.
Sprinkle the fish fillets thinly on both sides with the flour. Heat the remaining olive oil in a sufficiently large pan and fry the fillets on both sides over a moderate heat, but do not let them brown. Warm the sauce, but don't boil it. Drizzle the dressing over the upper part of the salad and place the finished fillets on the part of the salad without dressing.
Stir the pecorino into the sauce and spread it over the fish fillets, garnish and serve as a secondi piatti.