Preheat oven to 160C. Cut three JAZZ™ apples into wedges, then sauté with half the butter and the brown sugar in a frying pan over a low heat for 10 minutes, until softened, then set aside to cool completely.
Combine 250g (1¼ cups) hazelnuts, the flour, eggs, sour cream, cloves and caster sugar in the bowl of a food processor and pulse until a smooth batter forms. Transfer to a bowl then mix in the prunes and cooked Jazz™ apples. Spoon into a lined 24cm cake tin.
Finely slice the remaining Jazz™ apple and arrange on top of the batter. Roughly chop the remaining hazelnuts and melt the remaining butter. Combine these with the Demerara sugar and scatter over the apple slices. Bake for 50 minutes, until a skewer can be inserted and removed cleanly. Cool in the tin on a wire rack, then slice and serve.
