To make the filling, make fan shaped incisions into the apple quarters: With a small sharp knife make thin, deep lines on the back of each quarter. Set aside.
Preheat the oven to 200°C and grease a 26 cm springform pan.
For the cake combine flours, baking powder, sugars, and spices in a bowl and mix.
Add liquid ingredients and stir until no lumps are left in the batter.
Pour into the pan.
Prepare the streusel topping by combining all ingredients.
Knead with your hands until you can form large crumbs.
Place the apple quarters on the batter (incisions up) and place the streusel on top.
Bake for 40 to 45 minutes or until the cake is golden brown.
Let rest for five minutes, then remove from pan and let cool completely.