Preheat the oven to 180°C and grease a 20cm circular cake tin.
In a large mixing bowl, gently whisk together the sugar, melted butter, yoghurt, egg and rosewater. Break up any lumps where the ground almonds have stuck together and then stir them into the mixture. Then sift and fold in the flour. Lastly, very gently (so that they don't break up) fold the blackberries into the cake batter.
Spoon the mixture into the prepared tin. Pop into the oven to bake for around 20 minutes until risen, pale golden brown on top, and a skewer inserted comes out clean. If the top of the cake looks like it's browning too quickly, cover it with some tin foil for a few minutes to allow the inside to cook through fully. Remove from the oven and leave to cool in the tin for a few minutes before turning out onto a wire rack.
While the cake is cooling, make the frosting by beating the icing sugar into the cream cheese until smooth and well combined.
Once the cake is completely cool, ice it (just on the top) with the frosting using a palette knife.
Just before serving, decorate with a single sprig of blackberries (left on the branch). Alternatively, jumble a handful of blackberries with a few rose petals and loosely put them in the middle of the cake.