Preheat oven to 180 degrees Celsius. Grease and line the base and sides of a 20cm round cake tin.
Place whole orange in a food processor and process until pureed.
Add the flour, pistachio meal, sugar, butter, eggs and poppy seeds to the orange and process until just combined.
Spoon batter into lined tin and smooth surface. Bake in preheated oven for 55-65 minutes, or until a skewer inserted into the centre comes out clean. Remove cake from oven and allow to cool slightly in tin.
In the meantime, to make the syrup, zest the lemon and orange and set zest aside.
Into a measuring jug, juice the orange and lemon. Add water if needed until liquid totals 150mls.
In a small saucepan place sugar and sieved juice mixture. Place pan on stove over a medium-high heat and allow to boil for 5 minutes.
Add the zest and orange blossom and allow to boil for another 2-3 minutes.
While the syrup is boiling transfer cake onto a serving plate and, using a skewer, skewer holes into the top of the cake.
Once the syrup has reduced, pour slowly over the cake, allowing the cake to soak up the syrup. Arrange the candied zest over the cake and sprinkle with a few extra pistachios if you'd like.