In a small bowl mix the flour, baking powder, baking soda, and spices with a fork or spoon. Set aside. Tip: sift the baking powder and baking soda to eliminate any chunks.
Place the butter and sugar in a medium bowl and beat with a wire whisk or a hand blender till smooth and creamy
Add the eggs one at a time and whisk after each addition until they are well incorporated and the mixture is getting thick.
Add all the other wet ingredients, the sourdough, pumpkin, vanilla, oil, and maple syrup, as well as the salt if you used unsalted butter. Whisk together till smooth and creamy.
Dump the flour mix on top of the wet ingredients and fold it in gently and until just incorporated. I like to use a stiff silicone spatula for this. Do not over mix!
Pour half of the batter into your prepared pan.
Cover with half of the streusel mix.
Place the rest of the batter on top of the streusel and smooth the surface.
Cover with the rest of the streusel.
You could swirl it a little if you want streusel throughout the cake. I didn't and just used it as a topping.
Place the baking dish into the oven.
Bake until a toothpick comes out clean, or with just a couple of dry crumbs on it, about 45 minutes. Be sure to bake it through but don't over bake.
Take the cake out of the oven and place it on a cooling rack for 10-15 minutes before serving.