In a bowl, mix the flour with the water, oil, salt, and yeast until you get a smooth, uniform dough. Line a baking tray with parchment paper and spread out the dough. Top with the tomato purée and mozzarella, then roll it up and cut into 5 cm slices. Place each slice in a muffin tin.
Bake in a static oven at 200°C (390°F) for about 15 minutes.