Mix the ingredients and add just enough water for the dough to hold together. Knead to a smooth dough that no longer sticks to your fingers, adding more flour or water if needed.
Oil a large bowl, place the dough in it and turn over to coat with oil. Cover and let rise in a warm place until visibly risen in size, about 1 to 2 hours.
Fry the meat in a pan until evenly browned, breaking up any lumps. Let cool, then crumble. Set to the side.
Preheat the oven to 180 C / Gas 4.
Evenly press the dough on a pizza stone or baking tray to a make a thin base. Top the dough with enough sauce to thinly coat the dough all over. Scatter with the mince, arrange onions and tomatoes slices on top and lastly scatter the mozzarella.
Bake in the preheated oven until the dough is golden brown, about 15 to 20 minutes.