Preheat the oven to 180°C/gas mark 4. Line a baking tray with non-stick baking paper.
First make the tomato sauce. Heat the oil in a large saucepan set over a medium heat. Add the garlic and cook for 1 minute. Stir in the tomato purée and cook for 2 minutes before adding the tinned tomatoes. Bring to the boil, then reduce the heat and simmer for 15 to 20 minutes, until the sauce has thickened. Stir in the basil and simmer for a further 3 to 4 minutes.
Transfer the sauce to a blender and blitz until it’s your desired consistency, but watch out for any hot splashes. Alternatively, you could use a hand-held blender directly in the pan.
Place one tortilla on the baking tray and top with 2 tablespoons of the tomato sauce. Press the other tortilla firmly on top. Top with 2 more tablespoons of tomato sauce, then scatter over the cheese and pepperoni. Transfer to the oven to bake for 10 minutes, until the cheese has melted. Allow to cool before serving.