Preheat the oven to 180°C/160°C fan. Grease and line the base and sides of a 9-inch loose-bottomed round cake tin.
Place the diced apples, lemon juice, sugar and 50ml water into a saucepan. Cook over a medium heat for 5–6 minutes, or until the apples are just tender. Set aside to cool.
For the sponge, beat the butter and sugar together until light and fluffy. Add the vanilla, then beat in the eggs one at a time.
Sieve over the dry ingredients, add the milk, and gently mix until just combined.
Spoon the batter into the prepared tin and bake for 20 minutes.
Meanwhile, make the crumble by rubbing the flour, butter and sugar together with your fingertips until the mixture resembles coarse breadcrumbs.
Remove the cake from the oven and scatter over the cooled apples and raspberries. Sprinkle evenly with the crumble topping and return to the oven for a further 30 minutes, or until the crumble is golden and the cake is cooked through.
Leave to cool in the tin for 10 minutes before carefully removing. Serve warm or at room temperature with a generous spoonful of softly whipped cream.
