In a large bowl, add flour, baking powder and salt, and mix together.
With a fork or whisk stir in the oil.
Add the water and mix with your hands until a dough has formed.
Place dough on work surface, the dough should be soft but firm, if it is sticky add more flour, and knead for 2-3mins.
Wrap the dough up in cling film, to stop it forming a skin and inhibiting rising, and leave at room temperature for 30 mins.
While waiting chop up toppings.
Once 30 mins is up, preheat the oven to 220C.
Place the unwrapped dough onto a piece of greaseproof paper and roll out to about 10 inches in diameter.
Transfer to baking tray and add passata and toppings.
Turn the oven down to 200C and bake for 15 - 20 mins on the bottom shelf of the oven.