1. Heat oven to 180C. Grease a deep-sided 20-centimetre springform pan with the butter.

2. Peel the apples and cut into quarters. Cut out the cores and thinly slice. Toss with lemon juice and two tablespoons of the sugar, and set aside.

3. Using an electric mixer, beat the eggs with remaining sugar and vanilla extract at high speed for 7 minutes, or until ribbons form on the surface when you lift the beater. Sift the flour, cinnamon and baking powder and gently fold through the batter, until just-mixed. The batter will be quite thick.

4. Pile the apples into the base of the pan, and pour the batter over the top, to just below the rim of the pan (you may not need all the batter). Bake on the middle rack for one hour, until the top is crisp and an inserted skewer comes out clean.

5. Cool on a rack for 15 minutes, then remove the pan sides and transfer the apple cake to a serving platter. Dust with icing sugar and serve warm or at room temperature with the whisky toffee sauce. .

For whisky toffee sauce

1. Combine all sauce ingredients in a small pan and gently bring to the boil, stirring until smooth. Serve in a warm jug.