Begin by preheating your oven to 350 degrees F. Then, spray a 9x13-inch pan with baking spray. Set aside.
In a medium bowl, whisk together the flour, baking soda, baking powder, salt, and spices. Set aside. Then, in a large bowl, mix together the pumpkin, brown sugar, oil, egg, and maple syrup until blended. Pour the wet ingredients into the dry and stir until just combined. Do not over mix. Spoon the batter into your prepared baking pan. Spread evenly.
Next, make the crumb topping. In a small bowl, toss together the flour, brown sugar, salt and cinnamon. Cut in the cold butter using a fork or pastry blender. The mixture should be crumb-like. Sprinkle this mixture evenly over the top of the batter.
Bake for 30 minutes or until a toothpick inserted near the center comes out clean. Allow the cake to cool on a wire rack.
In the meantime, prepare your glaze. Whisk together the powdered sugar and pumpkin pie spice. Then whisk in the milk. If your glaze looks thick, add more milk, a teaspoon at a time. Drizzle the glaze over your cooled cake.