Whisk together flour, baking powder, baking soda, salt, and spices (cinnamon, cloves, nutmeg, and ginger) in a big bowl.
In another bowl, mix pumpkin, oil, brown sugar, milk, and maple syrup. Pour this wet mixture into the bowl from Step 3 and stir very gently until JUST blended.
Spread that batter into your prepared pan, then sprinkle the crumbly topping over the top, pressing it gently into the pumpkin cake batter.
Bake for about 30 to 35 minutes. After 30 minutes, stick a small toothpick in the middle — if it comes out mostly clean or with just a few crumbs, you're good to go. If it's still a bit gooey, wait for another 5 minutes.