Peel apples, quarter them and cut out the core. Roughly dice quarters. Sprinkle with lemon juice.
Put buttermilk into a measuring cup. Wash the buttermilk cup well and dry it. Measure 250 ml buttermilk, use the remaining buttermilk for other purposes. Put the butter, vanilla sugar, salt and sugar in a mixing bowl and whisk with the whisk of the hand mixer until foamy. Stir in eggs one at a time
Mix flour and baking powder and stir in alternately with 250 ml buttermilk. Add the poppy seed filling and stir in. Fold in apples. Put the dough into a greased, flour-spread baking tray (32 cm Ø at the top, 28 cm Ø at the bottom), smooth it down
Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 1 1/4 hours. After about 50 minutes of baking time cover the cake with aluminium foil. Remove the cake from the oven, place it on a cake rack and let it cool down. Stir icing sugar and 3-4 tablespoons of water until smooth. Pour into a piping bag, cut off the tip with sharp scissors and cover the cake loosely with it. Leave to dry
Remove from the mould and arrange. Smoothly stirred sour cream
waiting time 3 hours