Preheat the oven to 180°C. Grease and base line a 900g loaf tin.
Cream the butter, sugar and lemon zest until pale and fluffy. Whisk in the eggs, one at a time.
Mix together the flour and rose petals. Reserve one tablespoon of chopped pistachios and add the rest to the flour, then stir into the creamed mixture. Add the lemon juice and gently mix to combine.
Spoon into the prepared tin and bake for 40-45 minutes until golden and a skewer inserted in the centre comes out clean.
While the cake is baking, make the drizzle. Heat the lemon juice, sugar, rose petals, rose water and remaining pistachios until the sugar has dissolved, then allow to cool slightly.
Prick the hot cake with a skewer and pour the lemon drizzle over. Allow the cake to cool in the tin before removing. Garnish with the remaining lemon zest, extra chopped pistachios and a scattering of rose petals.
Whisk the crème fraîche with the honey and rose water until thickened, and serve with the cake.