For the tomato sauce, fry the onion and garlic in butter and olive oil until softened, then add the tomatoes, Italian seasoning, and salt and pepper to taste. Simmer until reduced to about 1 cup. Cool, then purée and set aside (this can be frozen for later use). For the pizza dough, place yeast, sugar, 2 tablespoons of the flour and 1/3 cup (80ml) warm water in a large bowl, mix to combine, and set aside in a warm place until bubbling (about 20 minutes). Using a wooden spoon, stir in the remaining flour, 1⁄2 cup warm water, oil and salt (you may need a little more water). Tip out onto a floured bench and knead for about 7 minutes until silky smooth. Wash and oil the bowl, then place dough in and turn it over so oiled side is facing up. Cover with plastic wrap (or a shower cap works well) and leave in a warm place until doubled in size (1–2 hours). Preheat a pizza stone on the hottest oven setting for at least 20 minutes. Punch dough down and divide into 2. Roll out on a floured board to very thin 30cm-diameter rounds. Coat a flat metal tray with cornmeal or semolina, place one of the rounds of dough on and spread with half the tomato sauce. Top with half the tomato slices, then tear up the mozzarella and place half the pieces evenly over the pizza. Slide onto the hot pizza stone and bake for about 12 minutes until the base is crisp and the mozzarella just melting. Scatter with half the basil leaves, drizzle with extra virgin olive oil and serve immediately. Repeat with remaining ingredients. SIMON SAYS: Use any leftover tomato sauce to dress pasta, or freeze it and save it for another Italian night at a later date.