Wash the apples, cut out the core. Cut apples into fine slices and put them back together again as an apple. Place in an ovenproof dish. Sprinkle with 4 tablespoons of lemon juice and rum. Spread butter in flakes on top.
Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 12 minutes. In the meantime peel and slice the bananas. Finely mash 100 g banana pieces, crème fraiche and 1 tablespoon lemon juice. Arrange apples on plates with some banana cream and remaining banana slices. Serve sprinkled with chocolate sauce