Spray a 9x9” glass baking dish with non-stick cooking spray and set aside.
Pumpkin Cake Layer:
In a medium mixing bowl, whisk together the dry ingredients (flour, pumpkin pie spice, cinnamon, baking soda, salt, and baking powder).
In a separate bowl, mix together the rest of the cake ingredients: eggs, oil, brown sugar, pumpkin puree, vanilla extract, and milk.
Fold the wet ingredients into the dry ingredients and stir gently to combine.
Spread batter into the prepared baking dish.
Make the streusel
In another medium bowl, whisk together the flour, baking powder, brown sugar, and cinnamon in a bowl.
Cut the butter into small pieces and use a pastry blender or fork to mix the butter into the flour mixture, just until the butter is pea-sized.
Stir in 1 tablespoon of milk or cream until the streusel clumps together just slightly. Sprinkle the streusel over the prepared cake batter.
Bake
Bake coffee cake 40-45 minutes. Coffee cake is done when a toothpick inserted into the center comes out with just a few moist crumbs on it.
Allow coffee cake to cool before adding glaze.
Whisk together glaze ingredients in a small bowl. Adjust the amount of milk added to make a nice, thick glaze that can be drizzled. Drizzle over the pumpkin coffee cake.
Cut into pieces and serve.
Notes
If the top of the cake seems to brown too fast, wrap the top with aluminum foil.
Do not swap the pumpkin puree for pumpkin pie filling. It is not the same and will ruin the balance of ingredients in your coffee cake!
Don't overmix the batter. A quick stir to just incorporate the wet and dry ingredients together will give you a tender crumb.
Make sure your baking powder hasn't expired. This is one of the agents to help the cake rise.