Preheat your oven to 350 degrees F. Grease a 9x13 inch cake pan with nonstick spray or butter.

Make the streusel: In a large bowl, whisk together 3 cups flour, 1 cup brown sugar, 1/2 cup granulated sugar, 1 teaspoon kosher salt, 1 tablespoon cinnamon, and 1 tablespoon pumpkin pie spice. Melt 1 cup of butter and stir into the mixture until it resembles wet sand. Chill if desired.

In a separate bowl, whisk together 2 and 1/4 cups flour, 1 and 1/2 cups granulated sugar, 1 tablespoon baking powder, 3/4 teaspoon baking soda, 3/4 teaspoon kosher salt, 1 tablespoon pumpkin pie spice, and 1 teaspoon cinnamon.

Chop 1/2 cup softened butter and add to the flour mixture. Mix until combined.

Add about half of the pumpkin puree to the mixture and mix until well combined.

In the bowl used for melted butter, whisk together the remaining pumpkin puree, 4 eggs, 1/4 cup vegetable oil, and 1 tablespoon vanilla extract. Gradually add this to the flour mixture in three parts.

Mix for about 20 seconds after each addition until light and fluffy.

Spread 2 cups of batter into the bottom of the prepared pan, followed by 1 cup of streusel. Add another 2 cups of batter, then 1 cup of streusel, and finish with the remaining batter and 2 cups of streusel on top.

Bake for 35 minutes, then add any remaining streusel on top and bake for another 10-15 minutes until a toothpick comes out clean.

Cool the cake on a wire rack for at least 15-20 minutes.

To make the icing, beat 1/4 cup butter until smooth. Add 1 teaspoon vanilla, 1/2 teaspoon kosher salt, 3 tablespoons milk, and 2 cups powdered sugar. Mix until smooth, adjusting the milk if necessary.

Drizzle the icing over the cooled cake. Serve warm and enjoy!