Place 2 of the oranges in a saucepan, cover with water, bring to a boil and simmer gently for 2 hours, topping up the water if necessary to keep the oranges covered.
Stir the saffron into 2 tablespoons of boiling water and set aside. Preheat the oven to 160C and grease a 23cm spring-form cake tin and line the base and sides with baking paper.
Drain the oranges and let cool a little. Remove any seeds from the oranges and then blend the whole fruit (including skins) in a food processor. Add 1 cup coconut sugar to the food processor, mix in, then add eggs, almond meal and saffron water and blend until combined.
Pour the mixture into the cake tin and bake for 60-80 minutes, until the cake is cooked through. Remove from the oven and let cool in the tin.
While cake is cooking remove the zest from the 3rd orange and cut into long, fine strips. Combine ¼ cup coconut sugar and ¼ cup water in a small saucepan and stir over a low heat until the sugar is dissolved. Add the orange zest and simmer for a couple of minutes. While the cake is still warm spoon over the zest and most of the syrup.
Once the cake has cooled, remove from tin and sprinkle over pistachios. Serve with cream, creme fraiche or yoghurt.