Step 1Cut the apples into quarters after washing them. Peel them and slice them thinly with a knife or a mandolin.
Step 2In a large bowl, break the eggs and whisk them with the sugar until the mixture turns white. In a small bowl, mix the flour mixed with baking powder.
Step 3Add it to the eggs with the melted butter, vanilla and rum (optional). Mix well with a rubber spatula. Add the slices of apples.
Step 4Pour the cake batter into a springform pan greased or covered with parchment paper. Sprinkle the top of the cake with sugar. The sugar will caramelize the top of the cake. Bake for 35-40 minutes at 180°C / 350 °F (fan oven).
Step 5While the cake is still warm, run a blunt knife along the edges of the cake. Unmold the cake and place it on a wire rack to let the cake cool. Place then on a large plate.