Preheat the oven to 325F and grease a 9x13 baking pan. Set aside.
For the streusel:
In a medium bowl, stir together the 1 cup brown sugar and 2 tsp cinnamon. Cut in the butter with two knives or a pastry cutter. Stir in the chopped pecans. Place in the fridge until needed.
For the pumpkin filling:
In a medium bowl, stir together the pumpkin puree, 1/3 cup white sugar, egg, cinnamon, nutmeg, ginger and salt until well combined. Set aside.
For the cake batter:
In a medium bowl, whisk together the flour, baking soda, baking powder and salt. Set aside.
In a large bowl with an electric mixer or the bowl of a stand mixer with a paddle attachment, cream the butter with the white sugar until light and fluffy, about 2-3 minutes. Mix in the vanilla. Add the eggs one at a time, beating well after each addition. Add the dry ingredients, alternately with the sour cream and mix until combined.
Spoon 1/2 of the cake batter into your prepared pan. Sprinkle with 1/2 of the streusel mixture. Spread all of the pumpkin filling over-top. Add the rest of the cake batter and spread on top of the pumpkin filling. Sprinkle the remaining streusel on top.
Bake in preheated oven for 45-55 minutes or until set and golden. Remove to a cooling rack and cool in pan until completely cooled.
For the glaze:
Stir together the icing sugar, milk and vanilla until you have an icing thin enough to fall from a spoon, adding more milk as necessary. When cake is cooled, drizzle over-top. Place cake pan in fridge to set glaze.
You can store the cake in the fridge or keep at room temperature, well covered.Be sure to read the "Cook's Notes" in the original post, for more tips, options, substitutions and variations for this recipe!