Preheat the oven to 180oC. Grease and base line a 20cm roundcake tin.
Sift together the flour, baking powder, sugar and cinnamon. Beat the eggs, oil, vanilla and yogurt together in a large bowl then fold in the flour mixture until just combined.
Stir the Walnuts and grated apple into the cake mixture and spoon into the prepared tin. Bake for 30-35 minutes until golden and a skewer comes out clean. Allow to cool before removing from the tin.
