Let the tomato cubes drain until all humidity has disappeared. Mix with the finely chopped basil leaves and season with vinegar, pepper and salt. Warm the olive oil to just below the boiling point and pour on the cold tomatoes.
Cut the white of the leeks into two to three centimeter pieces. Blanch in slightly salted, boiling water and cool in ice water. Do the same with the zucchini.
Fry the cod on the skin side for about ten minutes (depending on the size) in the oven preheated at 180 °C. Put the leeks in the oven for the last few minutes to warm them up.
Mix the zucchini with the passata and warm up.
Put the leek sprouts in some cold olive oil and heat until golden brown.
Set the plate. Place the zucchini in the center of the plate and place the cod on top of it. Finish off with a few dollops of sauce, some pieces of leeks, olives, tomatoes and leek sprouts.