In a medium bowl, whisk together flour, cinnamon, granulated sugar, light brown sugar, and salt. Stir in melted butter until combined and small crumbs form. Set aside.
Make the Pumpkin Bread
Preheat oven to 350 degrees F with rack in the middle position. Butter two, 1- to 1.5-pound loaf pans. Set aside.
In a stand mixer fitted with the paddle attachment, cream together butter, granulated sugar, and brown sugar until light and fluffy, about 3 minutes. Add eggs, one at a time, beating to combine after each addition.
Scrape the bowl and beat in the the vanilla extract and pumpkin puree. The mixture might look curdled; this is ok.
In a medium bowl, whisk together flour, cinnamon, nutmeg, ginger, cloves, baking powder, baking soda, and salt. Add to the pumpkin mixture in 3 additions, mixing until just combined. Stir in chopped pecans, if using.
Divide the batter between the two prepared pans. Top each with half of the topping, very gently pressing it into the batter.
Bake for 60 to 70 minutes, until a cake tester inserted into the center of the loaves comes out clean, or with just a few crumbs.
Let loaves cool in the pans for 20 minutes, then transfer to a wire rack to cool completely. Dust with powdered sugar, slice, and serve.
You can use light or dark brown sugar in the pumpkin bread batter and crumble. Dark brown sugar gives the batter a subtly deeper flavor, but will also mute the color of the bread a bit more. We enjoy the recipe with either. This pumpkin bread keeps well, tightly wrapped at room temperature, for up to 2 days; in the refrigerator for up to 5 days; and in the freezer for 2-3 months. For more info, reference the storage section in the blog post above.