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 butter in a medium bowl and pour it into the larger bowl. Stir until it looks like wet sand. Set aside and refrigerate if possible.

In another large bowl or stand mixer, combine 2 & 1/4 cups flour, 1 & 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 into chunks and add it to the flour mixture.

Open the pumpkin puree and add about half to the flour and butter mixture. Mix with a paddle attachment or beaters until everything combines.

In the same bowl where you melted the butter, add the rest of the pumpkin from the can, 4 eggs, 1/4 cup vegetable oil, and 1 tablespoon vanilla. Whisk well.

Add the egg mixture to the flour mixture in three parts, mixing for 20 seconds after each addition. Once all is mixed, beat an additional 1 minute until fluffy.

Spread 2 cups of batter into the prepared cake pan, followed by 1 cup of streusel. Add another 2 cups of batter, then another 1 cup of streusel, then finish with the last bit of batter and top with more streusel.

Bake in the oven for 35 minutes. Quickly remove the cake and sprinkle the remaining streusel on top. Return it to the oven for another 10-15 minutes. The total baking time should be 45-50 minutes, depending on your oven.

Let the cake cool on a wire rack for at least 15-20 minutes before cutting.

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 and drizzle over the cooled cake.