Begin by preheating your oven to 350°F (175°C). Grease a 9x13-inch baking pan with vegetable oil or non-stick spray.

In a medium bowl, combine flour, brown sugar, granulated sugar, salt, cinnamon, and pumpkin pie spice. Drizzle in melted butter and mix with a fork until the mixture resembles coarse crumbs. Chill briefly.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, salt, cinnamon, and pumpkin pie spice.

In another bowl, mix softened butter and pumpkin puree until crumbly. Add remaining pumpkin puree, eggs, vegetable oil, and vanilla extract, whisk until smooth.

Gradually pour the wet mixture into the dry ingredients, stirring gently until just combined. Pour half of the batter into the greased pan, add half of the streusel topping, repeat with remaining batter and streusel.

Place the pan in the preheated oven and bake for approximately 35 minutes. After this time, sprinkle any remaining streusel on top and continue baking for an additional 10-15 minutes.

Once baked, allow it to cool for 15-20 minutes in the pan. Prepare the sweet vanilla glaze by whisking together softened butter, milk, powdered sugar, and vanilla extract until smooth. Drizzle generously over the warm cake.