The recipe is calculated for an 18 cm springform pan, for a 26 cm springform pan double the amount and increase the baking time by about 10 minutes.
Melt the butter together with the white chocolate over low heat, then let it cool down a little and pour in the buttermilk. (If you use milk, mix it with a squirt of lemon juice and let it stand for approx. 10 minutes.)
Beat the egg with the sugar and vanilla sugar until very frothy. Pour in the buttermilk / chocolate liquid and mix. Add the flour and baking powder, mix briefly, stir in the almond well. Pour the batter into the mold. Place the peeled apples, cut into 4 mm thick wedges, in a wreath shape.
Bake at 165 ° convection for approx. 40 minutes, possibly cover the last 10 minutes.
Take the cake out of the oven and let cool down a little. Make a very thin glaze with the powdered sugar, vanilla sugar and water and brush it over the still warm cake.
Dust the cooled cake with icing sugar if you like.