Halve the mushrooms, depending on their size. Cut the onions into wedges, chop the garlic. White spring onion loin into 2 cm pieces, cut the rest into rings. Slice the olives and drain the tuna.
Heat the butter in a pan. Fry the mushrooms, onions and spring onions in it, turning. Add the garlic and season with salt and pepper. Unroll the pizza dough with the parchment paper and place on a baking sheet.
Sprinkle the pizza with half of the cheese. Top with tuna, tomatoes and mushroom mixture. Sprinkle with olives, oregano, salt, pepper and the rest of the cheese. Bake in a hot oven at 200 ° C for about 20 minutes.