Step 1

Preheat the oven to 170C/160C Fan/Gas 3½. Brush the bundt tin with melted butter, being careful to get into every corner, and dust with flour, shaking to coat the tin, then turn it upside-down and tap to remove excess flour.

Step 2

In a freestanding mixer, cream together the butter and sugar for about 5 minutes, until really pale and light (alternatively use a large mixing bowl and a hand-held electric mixer). Gradually add the eggs, mixing well and scraping down the sides of the bowl with a rubber spatula between each addition. Add the lemon and orange zests, juices and rosewater and mix again.

Step 3

Sift the flour, baking powder, bicarbonate of soda and cardamom into the bowl. Add the ground almonds, pistachios and soured cream and mix well. Spoon the mixture into the prepared tin and spread evenly using the back of the spoon.

Step 4

Bake for 35–40 minutes, or until the cake is well risen and a skewer inserted into the middle comes out clean. Leave to cool in the tin for 1–2 minutes, then carefully turn out onto a wire rack to cool completely.

Step 5

To decorate, beat the icing sugar with enough lemon and orange juice to make a smooth, thick but pourable icing. Add a few drops of rosewater to taste. Carefully spoon the icing over the cake, allowing it to run down the sides. Leave for 3–5 minutes for the icing to set slightly and then scatter with rose petals and pistachios. Leave to set completely before serving.