1. Preheat the oven to 200°C, gas mark 6. Wash the spinach well, then place in a large saucepan. Cover with a lid and cook for 2-3 minutes until wilted (do this in batches if your pan isn't big enough to fit all the spinach in one go).
2. Cool the cooked spinach under running water, then drain thoroughly. Squeeze to get rid of any excess liquid, then chop roughly.
3. In a large bowl, mix together the ricotta and eggs, then stir in the spinach, dill and salad onions.
4. Spoon half the mixture into an ovenproof pie dish, measuring 20cm x 30cm, then scatter over the cheese in an even layer. Top with the remaining spinach mixture.
5. Lay a sheet of pastry on the work surface and brush lightly with oil. Top with a second and third layer of pastry, brushing the top of each with oil. Place the pastry over the spinach mixture. Trim any excess and tuck in the edges. Using a sharp knife, score lightly in a crisscross pattern.
6. Bake for 40-45 minutes until golden brown and cooked through. Slice and serve with the salad and scattered olives.