2: Peel 1 kg apple, cut into quarters and remove the core.
3: Preheat the oven to 390°F (200°C). Choose a large non-stick pan that can go in the oven. Put on medium heat and melt 100 g butter, then add 100 g caster sugar. Leave until well mixed, stirring a little if necessary.
4: Add the apple pieces and pack tightly, though they should all be in contact with the butter and sugar mixture.
5: Leave to cook like this, simmering until the sugar begins to caramelize around the edge of the pan.
6: Turn the heat off and transfer the pan to the oven for about 20 minutes.
7: Take out of the oven and check that the apple pieces are all well soaked in the caramel; if not, return to the oven for a little longer.
8: Lay a sheet of cooking parchment on the worktop. Fish the burning-hot apple pieces out of the pan one by one (use 2 forks or tongs) and lay out on the paper. Leave to cool.
9: Put a layer of 300 g diplomat cream in the bottom of the tart case (a forcing bag is ideal for this).
10: Finish by arranging the tatin-style apple pieces on top of the cream. Your tart is ready.