Crumble the yeast into a small bowl and mix with sugar until the yeast is liquid. Put flour, salt, 2 tablespoons of oil and 250 ml of lukewarm water into a mixing bowl, add liquid yeast. Knead with the dough hooks of the hand mixer for about 5 minutes to a smooth dough.
Cover and leave to rise in a warm place for about 30 minutes.
In the meantime peel the onions and cut them into fine rings. Squeeze the mozzarella between two layers of kitchen paper, cut into thin slices. Finely slice Parmesan cheese.
Knead the yeast dough well on a floured work surface with floured hands. Cut the dough in half and roll out to a rectangle (approx. 39 cm x 26 cm).
Place a pastry base on a baking tray covered with baking paper (approx. 39 cm x 26 cm). Cover with mozzarella, place a second base on top. Spread onions on top, drizzle with 3 tbsp. oil. Season with pepper and sprinkle with parmesan.
Bake in the preheated oven (electric cooker: 250 °C/ convection oven: 225 °C/ gas: see manufacturer) on the lowest rack for 20-25 minutes. In the meantime, wash the marjoram, shake dry, sprinkle leaves and sprinkle over the pizza shortly before the end of the baking time.