Heat some olive oil in a large pan and add the chopped onion; cook for around 4 minutes until see-through. Add the spinach a handful at a time, it will quickly compact as it cooks creating space in the pan for more. Once you have added all the spinach, grind in some black pepper then set aside.
Mix the lamb with the sun-dried tomato paste and add enough white wine so you end up with a sticky, but not watery, mixture. Add the cinnamon, nutmeg and season with salt and pepper to taste.
Rub a little olive oil in a 2.5cm (1 in) deep, medium-sized baking dish and roll out the filo pastry. Line the dish with a layer of pastry, brush with olive oil then add another layer, letting the pastry overlap the dish and itself. Spread the ricotta over the pastry and add half the grated haloumi. Layer another couple of sheets of filo, oiling as before. Spread the spinach mixture out on this layer then cover with a couple more sheets of filo. On this, the topping, spread out the lamb mixture, then decorate with the sliced tomato. Sprinkle the remaining haloumi over the top with a drizzle of olive oil, bake in the oven for 25-30 minutes.