1. Preheat the oven to 220C/400F/gas mark 6. Peel and core the apples and chop into chunky quarters. Roughly slice the lemon. Place the apple slices into a container of cold water with the lemons to prevent browning.
2. Roll the pastry to the size of your frying pan, taking care not to make it too thin. Melt the butter in the pan on a low heat, spoon in the sugar, distributing it evenly, and let it boil until brown. Then add the apples.
3. Carefully lay the rolled pastry on top of the apples and leave for 1 minute. Then place the pan into the oven for 15 minutes or until the pastry starts to puff and go crispy.
4. To remove the tart, take a large plate and place it on top of the pan. Flip the tart on to the plate and leave to cool before cutting.
Tip: Serve the tart tatin with vanilla ice-cream and sprinkle with icing sugar and a sprig of mint. Alternatively, if its a cold, autumn night, serve with some hot custard.