Preheat oven to 160 C fan/ 180 C and lightly grease and line a 22 cm round cake tin.
Cream together the butter and sugar until light and fluffy and then add the eggs, one at a time, with a spoonful of the flour, beating well.
Sift over the flours, raising agents, spices and salt and add the yogurt. Beat well and spoon into the prepared baking tin.
Peel, core and finely slice the apples, arranging in a circular pattern starting from the outside and working your way in to the centre.
Sprinkle with extra cinnamon and bake in the centre of the oven for 30-35 minutes (according to the original recipe). My fan oven required an hour to bake the cake fully.
Leave to cool in the tin for 10 minutes before transferring to a wire rack to cool completely. Store in an airtight tin for 2-3 days.