Pre-heat oven to 180°C /160°C (fan forced). Line a lamington pan with baking paper
Combine cake mix with melted margarine or butter and coconut. Mix to resemble fine crumb. Press into prepared lamington pan and bake for 20 minutes. Spread base with pie apples.Whisk together sour cream and eggs and pour over apples. Sprinkle top with sachet of cinnamon sugar
Bake for a further 30 minutes or until top is set and golden. Cool and refrigerate