Preheat oven to 350.
Drain the cashews and place in blender along with banana, tofu, white sugar, 1/3 c brown sugar, oil, arrowroot, lemon juice, vanilla, orange, and salt. Blend until very smooth.
Transfer ¼ c of this to a bowl and set aside, then add pumpkin and spices to the batter still in the blender and blend well.
Spread pumpkin batter evenly over the crust, then drop spoonfuls of reserved batter all over the top. Use the spoon handle to swirl the two batters together for a marbled effect.
Bake for 25 minutes.
Meanwhile, place remaining 1/3 c brown sugar in medium bowl along with margarine and a dash of salt. Cut the margarine into the sugar until the mixture resembles chunky wet sand, then stir in the pecans.
Remove the cheesecake from the oven, cover evenly with sugar-pecan mixture, and bake another 20-25 minutes, until slightly puffy and golden around the edges.
Let cool, then refrigerate for at least 3 hours (ideally overnight).