Set aside 7-8 pecan halves and chop remaining pecans. Peel, halve and core apples and cut halves several times crosswise on convex side. Stir soft butter with salt, vanilla sugar and sugar until fluffy, gradually add eggs and continue to beat until mixture is frothy. Combine flour with baking powder, sift over frothy mixture and stir.
Pour mixture into springform pan lined with baking paper and smooth surface. Arrange apples on dough and press lightly. Sprinkle with chopped pecans and bake in a preheated oven at 180°C (approximately 350°F) for about 30 minutes.
Meanwhile, brush pecan halves with apple juice, roll in sugar and spread on edge of the cake. Bake cake another 20-30 minutes (until toothpick inserted in center comes out clean,) remove from oven and let cool slightly. Remove cake from pan and let cool on a wire rack.