Sift the flour and salt into a bowl, add the yeast and mix well. Make a well in the centre and add the measured water and oil. Stir until it forms a wet dough, then beat for 2 minutes. Turn the dough out on to a well floured surface and knead for about 2 minutes until it becomes smooth and elastic. Roll out to a 30 cm (12 inch) circle, and place on a lightly oiled baking sheet. Cover with lightly oiled clingfilm and leave in a warm place while making the topping.
Heat 1 tablespoon of the oil in a small frying pan and cook the onion over a moderate heat for 2–3 minutes. Remove from the heat and add the passata and tomato purée. Spread over the pizza base to within 2.5 cm (1 inch) of the edges, and scatter over the ham.
Toss the pineapple with the remaining oil. Scatter it over the ham, then top with the mozzarella. Bake in a preheated oven, 220°C (425°F), Gas Mark 7, for 15–18 minutes until golden. Scatter with thyme leaves, if liked.