Preheat your oven to 350°F (175°C) and grease a 9x13-inch pan.

Combine 3 cups flour, both sugars, salt, cinnamon, and pumpkin pie spice in a bowl. Gradually add melted butter to form coarse crumbs.

In a large bowl, whisk the remaining flour, brown sugar, granulated sugar, salt, cinnamon, and pumpkin pie spice.

Add cold butter chunks and pumpkin puree, mixing until incorporated.

Mix remaining pumpkin puree, eggs, vegetable oil, and vanilla extract in a separate bowl until smooth. Fold gently into the flour mixture.

Spread 2 cups of batter in the prepared pan, sprinkle 1 cup of streusel topping, layer with 2 cups of remaining batter, and top with remaining streusel.

Bake for 35 minutes, checking for doneness with a toothpick. Continue baking if necessary.

Let the cake cool before preparing the glaze by mixing butter, powdered sugar, vanilla, and milk until smooth. Drizzle over the cooled cake.