Preheat the oven to 200°C. Line a baking sheet with baking paper.
1. Relish Heat the oil in a deep pan and fry the onions until soft. Add the garlic and chilli (if using) and stir-fry until fragrant. Add the tomatoes and stir-fry for a minute, then add the rest of the ingredients except the salt and pepper. Simmer slowly for 10 minutes, stirring occasionally to prevent catching. Season with salt and pepper and set aside to cool.
2. To finish Put one naan bread on the prepared baking sheet, spoon some of the relish on top and spread evenly. Put some basil on top, followed by mozzarella slices and salami slices. Sprinkle the Parmesan cheese over.