Preheat the oven to 350 degrees. Grease 8 silicone molds
In a food processor, pulse the pistachios to make a powder.
In a large bowl, mix together the sunflower oil and caster sugar.
Add the eggs, vanilla paste, ground cardamom and lemon zest. Stir until combined.
In a separate bowl, add the flour, ground pistachios, ground almonds, salt, baking powder and baking soda. Stir until well combined then fold into the wet ingredients in the other bowl.
Fold in the sour cream.
Pour the mixture into the prepared molds and bake for 35 – 40 minutes, or until a skewer inserted comes out clean.
In the meantime, prepare the syrup. Heat the lemon juice and sugar in a saucepan until the sugar is dissolved, then briefly bring to the boil.
Remove from the heat and set aside.
As soon as the cake is cooked, poke holes all over the top using a skewer.
Pour over two-thirds of the hot syrup and leave to cool in the tin for 5-10 minutes. Add half the extra pistachios (for decorating the cake) to the remaining syrup.
When the cake is cool, remove it from the tin.
For the lemon icing, sift the powdered sugar into a bowl and stir in the lemon juice until smooth.
Drizzle over the cooled cake.
To finish, finely chop the remaining pistachios and scatter over the icing. Top with the syrup-coated pistachios and some dried rose petals.