Roughly chop the nuts. Melt 100 g butter in a pot. Add 75 g brown sugar and maple syrup and melt at low heat as well. Stir in nuts. Line a square springform pan (24 x 24 cm) with baking paper.
Pour in nut mixture and smooth it down. Cream 200 g butter with the whisk of the hand mixer. Add 150 g brown sugar, vanilla sugar, lemon peel and salt bit by bit and mix to a smooth mixture. Stir in the eggs one by one. Mix flour and baking powder, pass through a sieve and stir in 2 portions. Finally, stir in yoghurt. Spread the dough over the nut mixture. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 3) for approx. 25 minutes. Take out and remove the cake edge from the baking frame with a knife.
Mix flour and baking powder, pass through a sieve and stir in 2 portions. Finally, stir in yoghurt. Spread the dough over the nut mixture. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 3) for approx. 25 minutes. Take out and remove the cake edge from the baking frame with a knife. Turn over the cake, remove baking paper