Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.
In a large bowl, whisk together the flour, sugar, baking powder, baking soda, salt, and pumpkin pie spice.
In a separate bowl, mix the pumpkin puree, eggs, and melted butter until well combined.
Gradually add the wet mixture to the dry ingredients, stirring until just combined.
Pour the batter into the greased baking dish and smooth the top with a spatula.
Bake for 30-35 minutes or until a toothpick inserted comes out clean.
While the cake cools, whisk together the powdered sugar, milk, and vanilla extract in a small bowl.
Once the cake is slightly cooled, drizzle the gooey topping evenly over the surface.
Let the cake sit for at least 30 minutes before slicing.