Martha Collison's plum streusel cake

Preheat the oven to 170°C, gas mark 3. Grease and line the bottom of a chiffon cake pan with baking parchment or grease a 22cm ring tin.

Cream together the butter and sugar until light and fluffy, then add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract, then add the flour and beat until a smooth batter forms, then set aside.

To make the topping, put the sugar, butter and flour into a small bowl. Using your fingers, rub the cubes of butter until the mixture is crumbly and only very small chunks of butter remain. Stir through the crushed amaretti biscuits and set to one side.

Spoon the cake batter into the tin and spread out using a spatula, then arrange the sliced plums evenly over the top. Sprinkle the topping over the plums and bake in the preheated oven for 35-40 minutes. A skewer inserted in the centre should come out clean and the topping should be golden brown in colour. Cool slightly before removing from the tin.