Preparing the dough: Take your dough out of the freezer and place the jars in a tall bowl with hot water. Let it thaw and rest for 1 hour and 50 minutes.
Debone the mackerel so that you have no skin or bones left, just the pieces of fillet.
Peel the onion and slice it thinly with a mandoline. Place in a bowl and pour the vinegar over it.
Grate the Parmesan cheese.
Stretching the dough: Put 3 tbsp of semolina in each jar. Use plenty of flour to prevent the dough from sticking. Scrape with your fingers around the sides downwards. Place the dough on the table with all the flour. Start stretching from the center outwards, always staying 1 cm from the edge. Lift it now and remove excess flour.
Spread a spoonful of pesto on one half and sprinkle the grated mozzarella over it. Fold it over, press the edge slightly, and bake for about 5 minutes in a preheated pizza oven (between 380-430°C).
Turn it on its axis to cook and color evenly. Take it out.
Filling the sandwich: Open the pizza sandwich again and fill it with the tomato slices, pieces of mackerel, arugula, pickled onion, and Parmesan cheese. Finish with chili oil.
Tips
Oven: If you bake in a normal oven, use a pizza stone. Place the oven on hot air and grill. Let it heat up well for at least 20 minutes. The hotter the oven, the better the result. You can also turn a baking sheet and preheat well, in the highest place just below the grill.