Preheat the oven to 190°C and grease two 20cm loose-bottomed tins.
Cream the butter, sugar, and salt until pale.
Whisk eggs and gradually add to the butter mixture with vanilla.
Fold in the flour and divide the batter between the tins.
Bake for 25–30 minutes until golden and well-risen.
Cool cakes on a wire rack and remove the parchment.
Dissolve 500g of raspberries, jam sugar, and lemon juice in a pan.
Boil the mixture for 5 minutes and then set aside to cool.
Whip the double cream and transfer it to a piping bag.
Assemble the cake with jam, piped cream, and fresh raspberries.
Top with the second sponge and dust with icing sugar.