Beat the butter, caster sugar, ground cinnamon, and vanilla until smooth and creamy. Add the eggs and milk and beat until combined. Sift in the self-raising flour and beat until just combined. Pour the mixture into the prepared tin.
Sift in the self-raising flour and beat until just combined. Pour the mixture into the prepared tin.
Cut the peeled apples into four sections and make deep slits in each section. Place the apples (round side facing up) onto the cake batter and press down lightly.
Sprinkle over the ground cinnamon and the raw sugar. Bake in the oven for 40-45 minutes or until the cake is cooked when tested with a skewer.
Leave to cool in the baking pan for 20 minutes before placing it onto a wire rack to cool completely.