Preheat the oven to 200°C. Heat a baking tray or pizza stone.
Finely chop the onion, tomatoes and the parsley. Put these in a bowl and mix with the lamb, oil and Harissa. Keep back some of the parsley. Season to taste.
Put a flatbread on the hot baking tray and spread about 3-4 Tbsp of the mixture over it. Cook for about 8 minutes until the flatbread is golden and crispy. Then bake the other ones.
Serve with the remaining parsley scattered on top and some lemon juice squeezed over it - then fold in half.