Preheat the oven to 350°F. Spray a 9" x 13" pan with nonstick cooking spray. (For a thicker cake use an 8x8 or 9x9 inch pan. SEE NOTES). Set aside. In the bowl of a stand mixer add the flour, sugar, brown sugar, baking powder, baking soda, pumpkin spice, cinnamon, and salt. Whisk to combine.
Add the egg, vegetable oil, milk, pumpkin puree, and vanilla. Using the paddle attachment on medium low speed, mix until the wet ingredients are incorporated.
Using a spatula, spread the batter into the prepared pan.
Whisk the flour, sugar, and cinmamon in a medium sized bowl. Add the butter and using a pastry blender cut the butter into the mixture until the butter is the size of small peas. Stir in the chopped pecans.
Evenly distribute the streusel mixture over the cake batter. Bake for 22-25 minutes. The cake is done when a toothpick is inserted into the center and it comes out clean, or with a few moist crumbs on it. Let the cake cool for 15-20 minutes before topping with the glaze.
Prepare the glaze by whisking all of the glaze ingredients in a small bowl. Add more milk or more powdered sugar to your liking. You want the glaze a thick, syrupy-like consistency. Using a spoon, carefully drizzle the glaze over the cake. Serve the cake warm or at room temperature.