Preheat your oven to 350°F.
Cream together the butter, brown sugar, and white sugar.
Add the pumpkin, vanilla, and milk to the mix and stir to combine.
Add the flour, baking powder, cinnamon, pumpkin pie spice, cream of tartar, and salt. Mix until well combined. Warning: it'll be sticky!
Grease a 9x13 baking dish. Spread the batter as evenly as you can inside it.
Sprinkle your topping across the top of the batter.
Bake for 20-25 minutes. You're looking for a soft but not raw center, similar to brownies. Let cool and serve!