Preheat the oven to 200C/180C Fan/Gas 6 and place a large baking tray upside-down on a shelf.
To make the dough, sift the flour and baking powder into a large bowl.
Add the salt and a pinch of pepper, then stir in the oil.
Make a well in the centre, then stir in the warm water and mix to a soft dough, drawing the flour in from the side of the bowl a little at a time. Ideally you want to end up with a soft and slightly sticky dough.
Put the dough onto a lightly floured work surface and knead for 2 minutes, until smooth and springy.
Place a sheet of greaseproof paper on the work surface, then dust with a little flour and place the dough on top of it.
Carefully roll the dough out into a 30cm/12in disc, roughly the thickness of about 5 mm.
Slide the dough and the paper onto the hot baking tray in the oven.
Bake for 3 minutes.
Meanwhile, pour the passata into a bowl, add the tomato purée, mixed herbs, sea salt and black pepper and mix thoroughly.
Remove the dough tray from the oven.
Cover the base with the tomato sauce, using the back of a spoon, leaving a small gap around the edges of the dough.
Scatter the mozzarella over the tomato sauce, then top with the pepperoni and cheddar.
Add any other topping you like at this stage.
Bake for 15 minutes, or until the base has puffed up and is cooked through and the cheese is golden and bubbling.
Cut into wedges with a pizza cutter and serve immediately.