• Pre heat the oven to 350 degrees. Lightly grease and flour a 9 inch springform pan. To make the baked cake easier to remove from the pan lightly grease the pan, line the bottom with parchment paper and lightly grease the parchment paper. Dust the pan with flour.
• For the Nut Topping:

  Place the nuts, brown sugar and cinnamon in a small bowl, stir to combine and set aside.

For the Filling:

• Combine 1/3 cup flour and 1/4 cup butter into a medium bowl. Cut the butter into the flour using a pastry blender until it resembles coarse crumbs.  Add 3/4 cup of the nut topping mix and stir to combine. Toss the apples with lemon juice and set aside.

Cake Batter:

• Combine the flour, baking powder, baking soda and salt in a medium bowl.  Stir together to combine. Set the bowl aside.

  Place the butter and sugar into a large bowl. Using an electric mixer , beat the two together until they are light and fluffy. 

  Add the eggs to a bowl one at a time and beat until well incorporated. 

  Add half the flour mixture to the bowl, beating until it's just incorporated. Add all of the sour cream to the bowl and mix until just incorporated. Add the remaining flour to the bowl and mix until just incorporated.

  Spread 2/3 of the cake batter into the prepared 9 inch springform pan. Sprinkle the filling mixture over the batter.Layer the apples over the filling. Gently spread the remaining batter over the apples. Sprinkle with the topping mixture.

  Bake for 60 minutes or until a toothpick inserted in the center of the cake comes out clean.

  Cool on a wire rack for 15 minutes,  loosen the side of the pan then remove the cake from the pan and finish cooling on a wire rack.