Preheat oven to 350°F, and grease or line an 8x8 inch pan with parchment paper.
Make the streusel:
In a medium bowl, mix together flour, brown sugar, granulated sugar, cinnamon, and salt.
3/4 cup all-purpose flour, 1/3 cup brown sugar, 2 tbsp granulated sugar, 1 tsp cinnamon, 1/4 tsp salt
Pour melted butter over the dry ingredients and stir until crumbly. It's ok if you have bigger chunks, don't try to break them up. Place the streusel in the fridge for later.
1/4 cup unsalted butter melted
Make the Cake
In a medium bowl, whisk together the flour, baking powder, baking soda, pumpkin pie spice, and salt.
1 ¾ cups all-purpose flour, 1 tsp baking powder, ½ tsp baking soda, 1 tbsp pumpkin spice, ¼ tsp salt
In a separate large bowl, whisk together sugar, oil, eggs, pumpkin puree, and vanilla until smooth.
1 cup brown sugar, 1/4 cup granulated sugar, 2/3 cup vegetable oil, 2 large eggs, 1 cup pumpkin puree, 1 tsp vanilla extract
Pour the cake batter into the prepared pan and spread evenly. Sprinkle the streusel evenly on top of the batter.
Bake for 45-55 minutes, or until a toothpick inserted into the center comes out clean.
Make the Glaze
In a medium bowl mix the powdered sugar, butter, vanilla bean paste, salt, and milk and mix until combined.
1 tablespoons butter very soft, 1/2 teaspoon vanilla bean paste, 1/4 teaspoon salt, 1 tablespoon milk, 2/3 cup powdered sugar
Drizzle on top of the cooled down pumpkin cake before slicing and enjoying. I also like to let the icing set before slicing for a neater presentation.