Combine the nuts, brown sugar, and cinnamon to make "nut mixture."
For "topping" cut the 3 Tbsp of butter into 1/3 cup flour to make course crumbs and then stir in 3/4 cup of the nut mixture. Set nut mixture and topping aside. Soak the pear slices in the 2 tspn of lemon juice.
Combine flour, baking powder, baking soda and salt. Set aside. Whisk together oil, sugar, vanilla and eggs. Add flour mixture and sour cream alternatively to the oil mixture to make a batter. Spread two-thirds of the batter into the prepared pan. Sprinkle with reserved nut mixture. Layer pears over the top. Gently spread remaining batter over the pears. Sprinkle with reserved topping.
Bake for 60 minutes or until a wooden toothpick inserted in the center comes out clean. Cool in pan on a rack for 10 minutes, before removing the side of the spring form pan. Once cooled slightly dust with confectioners sugar and serve with the whipped almond cream.