To make the topping: In a medium size mixing bowl, whisk together the sugars, cake flour, pumpkin pie spice, salt and pecans. Pour in the melted butter and stir with a spatula until a thick crumble forms. Allow to sit while preparing the remainder of the cake.
To make the cake: Preheat oven to 350 degrees. Spray an 8-inch or 9-inch square baking dish or round springform pan with baking spray, set aside. NOTE: you can use parchment paper in the square dishes for easier removal. You will need to lightly spray it with baking spray.
In a large mixing bowl or the bowl of a stand mixer, beat the oil, sugars, pumpkin puree, sour cream and vanilla extract. When the mixture is smooth, add the eggs one at a time.
In a small mixing bowl whisk together the flours, baking soda, baking powder, salt and pumpkin pie spice. With mixing speed on low, gradually add the the dry ingredients, mixing just until combined (overmixing will create a dry tough crumb. You can use a spatula to fold in the dry ingredients if you wish- no more than 20 strokes/folds.
Pour the batter into the prepared pan, spreading into an even layer. Cover with the crumb mixture. You will have to break the crumbs into smaller pieces.
Place in the oven and bake for 30-40 minutes or until a cake tester inserted into the center comes out clean, and the center of the cake just barely jiggles (note that baking time will vary depending on the type and size of the pan you use). Remove from the oven and allow to cool in the pan for at least 30 minutes before slicing and serving. Top with a dusting of powdered sugar if desired.
-You could definitely add chocolate chips or cranberries to the cake base! I'd suggest 1/2 c. of mini chocolate chips or 3/4 c. quartered cranberries. Fold them in along with the dry ingredients.