For the apple tart, peel apples, cut in half, core and cut several times at the bulge. Cream butter, sugar, eggs and lemon zest.
Mix flour with baking powder well and gradually stir in until the mixture is very fluffy. Preheat oven to 180 °C.
Grease and flour the cake tin. Pour in mixture and top with apples with the bulge facing up. Mix jam with rum and stir until smooth.
Brush the apples with it and bake the apple tart for 45 minutes until light yellow.