Mix butter, sugar and vanilla extract for approx. 8 minutes with the whisk of the hand mixer until creamy. Stir in the eggs one by one. Stir in almonds. Mix flour and baking powder and add the milk in portions alternating with the almonds.
Line the bottom of a springform pan (22 cm Ø) with baking paper. Fill in the dough and smooth it down. Wash, quarter, core and cut apples into thin slices. Arrange the apple slices in a fan shape. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 35-40 minutes. Remove from the oven, leave to cool in the pan for approx. 15 minutes, then turn out onto a cake rack and allow to cool. Dust with icing sugar if necessary