Preheat your oven to 350 degrees F. Grease a 9×13 inch cake pan with nonstick spray or butter.

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 into the larger bowl, stirring until combined. Set aside or refrigerate.

In a large bowl or stand mixer, whisk together 2 and 1/4 cups flour, 1 and 1/2 cups 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 it to the flour mixture.

Add about half of the pumpkin puree (from the can) to the bowl with the flour and butter.

Using a paddle attachment or electric beaters, blend the mixture until it forms a ball. Add more pumpkin puree if needed.

In the same bowl used for melting butter, whisk together the remaining pumpkin, 4 eggs, 1/4 cup vegetable oil, and 1 tablespoon vanilla until combined.

Add the egg mixture to the flour mixture in 3 additions, mixing well after each addition until the batter is light and fluffy.

Spread 2 cups of batter into the prepared cake pan.

Sprinkle 1 cup of streusel evenly over the top, then spread another 2 cups of batter on top.

Add another 1 cup of streusel on top and finish with the remaining batter.

Spread another 2 cups of streusel over the top of the cake.

Bake at 350 degrees F for 35 minutes.

Quickly sprinkle the remaining streusel on top of the cake and return it to the oven.

Bake for an additional 10-15 minutes until a toothpick comes out clean.

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

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

Drizzle over the cooled cake or individual slices.