Step 1

Position a rack in the centre of the oven and preheat to 180C or 160C fan-forced. Grease a 23cm springform pan with the butter.

Step 2

In a medium bowl, toss the apples with Grand Marnier to coat, and set aside.

Step 3

In another medium bowl, whisk together the flour, caster sugar, baking powder, salt and 1/4 teaspoon of cinnamon. In a large bowl, whisk together oil, milk, whole eggs, orange zest and vanilla to blend. Whisk dry ingredients into the wet ingredients to form a smooth batter. Be careful not to over-mix.

Step 4

Transfer 1 cup of the batter to a small bowl and mix in the extra flour; set aside. Whisk egg yolks into remaining batter in the large bowl just to blend. Stir in the apples. Transfer the apple batter to prepared pan and, using a crank-handled spatula, spread batter into an even layer and press the apples in to submerge them. Pour the reserved batter evenly over the apple batter. In a small bowl, whisk the extra caster sugar and 1/2 teaspoon cinnamon to blend, and then sprinkle it evenly over the batter.

Step 5

Bake for 50 mins, or until a skewer inserted into the centre of the cake comes out clean and the top is golden brown. Transfer the pan to a wire rack and cool for 15 mins. Run a knife around the sides of the cake and release the pan sides. Cool cake for about 30 mins to serve warm, or cool completely. Dust with icing sugar.

Step 6

In a medium bowl, whisk 1 cup thickened cream and 1 tbsp icing sugar, sifted until thick. Dust the cake with 1 tsp icing sugar, sifted. cut cake into wedges and serve with a generous dollop of whipped cream.