1. Preheat the oven to 180C (160C fan) and grease a deep 20cm round cake tin with a little butter and line the base with parchment paper.
2. To make the cake place the pistachios into the bowl of a food processor and pulse until finely ground (to prevent the nuts forming a paste you can add a tbsp of the flour to the processor).
3. Place the butter into a large bowl and, using an electric mixer, beat until light and creamy about 3 minutes. Add the sugar and the orange zest and beat together until light and fluffy, about 5 minutes.
4. Add the eggs a little at a time, beating until fully combined. Sieve the flour, baking powder and salt together, add the pistachios and mix together. Add the dry goods to the butter mixture and gently fold together until combined. Scrape the batter into the prepared tin and gently level out
5. Bake the cake in the preheated oven for 50-55 minutes or until the cake is golden brown and when a skewer inserted into the middle of the cake comes out clean, if the cake is browning too quickly lightly cover with a piece of foil.
6. Allow the cake to cool in the tin for 10 minutes before turning out onto a wire rack to cool completely. To finish the cake sprinkle with extra chopped pistachios and the seeds from a pomegranate.
7. Because this cake is made with ground nuts it keeps brilliantly, at least 4 days if kept in a sealed container.