Preheat oven to 180 C (350 F) standard / 160 C (320 F) fan-forced.
Grease and line an 8 or 9 inch round cake tin with baking or parchment paper.
In a large mixing bowl, add flour, baking powder, baking soda and sugar.
Add chopped apple and stir briefly to combine.
In a separate bowl, add eggs, vanilla, oil and yoghurt.
Whisk briefly just to break up the egg yolks.
Add wet ingredients to dry ingredients and gently mix with a wooden spoon until combined – but be careful not to over mix.
Spoon batter into prepared tin.
To make cinnamon topping, combine cinnamon, sugar and butter.
Mix together until lumpy and wet.
Sprinkle over cake batter.
Bake cake for approximately 30-35 minutes or until a skewer inserted into the middle comes out clean.
Transfer cake to a wire rack to cool completely.
To make the glaze, mix together sugar and 1 tablespoon of milk.
Stir until smooth. If the glaze is too thick, add an extra tablespoon of milk.
Drizzle glaze all over the cake.