Heat oven to 180C/160C fan/gas 4. Butter a deep, 20cm round cake tin and line the base and sides with baking parchment. Put the whole hazelnuts, plus 1 tbsp each of the sugar and flour, into a food processor and whizz until the hazelnuts are as fine as you can get them.
Add the butter, remaining sugar and eggs to the processor, then tip in the vanilla, spice, ¼ tsp salt, remaining flour and baking powder. Whizz until smooth. Remove the blade, then stir in the grated courgettes, apple and dried fruit.
Spoon the mix into the tin, smooth the top, then scatter with the chopped hazelnuts, pressing them into the batter a little. Bake for 1 hr 10 mins (see tip, below), covering the top loosely with foil after 45 mins, until the cake is risen and golden. Cool in the tin for 20 mins, then remove and cool on a wire rack.