Wash the tomatoes, quarter them, remove the seeds and cut them into small cubes. Peel and finely dice the onion. Grate cheese
Lightly dust a clean tea towel or a large sheet of baking paper with flour. Unroll the pizza dough and place it with the dough side on the tea towel. Peel off the baking parchment. Spread the dough with tomato sauce, leaving an approx. 2 cm wide edge on both long sides. Sprinkle oregano on the sauce. Spread tomatoes and onion on top and season with pepper (no salt!). Cover with Parma ham and sprinkle with 2/3 grated cheese
Moisten one long side edge with water. Then roll up the pizza from the opposite long side. Press the edge of the dough well. Cut the pizza roll into approx. 10 thick slices. Grease a pizza tray and dust with flour. Put pizza snails in the form and sprinkle with the remaining cheese. Bake in the preheated oven on the lower shelf (electric oven: 225 °C/ convection oven: 200 °C/ gas: level 4) for approx. 25 minutes