Heat oven to 180C/160C fan/gas 4. Lightly grease two 20cm cake tins and line with baking parchment. In a large mixing bowl, beat the butter and sugar together until pale and fluffy. Gradually add the eggs a little at a time, scraping down the side of the bowl after each addition. If the mixture starts to curdle, add 1 tsp flour. Add the vanilla extract, mix in half the flour, then fold in the rest.
Divide the mixture between the cake tins and bake for 20-25 mins – a skewer inserted into the middle of the cakes should come out clean. Leave to cool in the tins for 10 mins, then turn out onto a wire rack to cool completely.
Meanwhile, make the filling. Whisk the cream to soft peaks, adding the rosewater as you go, then fold in the jam, being careful not to over-mix.
Place one of the sponges on a serving plate and top with the cream mixture. Scatter with the raspberries, then top with the other sponge.
For the icing, mix together the icing sugar, 2 tbsp water and the rosewater, and stir in the juice from a few crushed raspberries. Drizzle over the cake, arrange the rose petals and the remaining raspberries on top and dust with icing sugar.