Apple, caramel and hazelnut traybake

• 200g skinless hazelnuts

• 200g butter, room temperature

• 200g caster sugar

• 3 medium eggs

• 4 tbsp yogurt

• 200g self-raising flour

• 1/2 tbsp baking powder

• 1 1/2 eating apples, cored and cut into thin slices (each 1/2 into 16)

• 1 tbsp icing sugar, sifted

For the topping

• 75g butter, room temperature

• 75g soft light brown sugar

• 3 tbsp double cream

• 85g hazelnuts, roughly chopped

• 1/2 eating apple, cored and sliced into thin wedges

1. Preheat the oven to 180°C/fan oven 160°C/gas mark 4. Lightly grease a square loose-bottomed 20x20cm cake tin and fully line with baking parchment.

2. Finely grind the hazelnuts in a mini processor. Put the butter and sugar in a bowl and cream together with a wooden spoon. Whisk in the eggs and yoghurt until fluffy. Sift the flour and baking powder together and fold in with the ground hazelnuts.

3. Fold in the sliced apples and spread the mixture evenly into the tin. Sift over the icing sugar. Put the tin on a baking tray and cook for 1 hour.

4. Meanwhile prepare the topping. Put the butter, sugar and cream into a small pan and melt together. Stir in the nuts and fold in the apple.

5. Spread the mixture over the cake when it has cooked and put back in the oven to bake for a further 10-15 minutes.

6. Put the tin on a wire rack to cool. When still warm lift out of the tin and serve warm or cold.