MAKE THE BATTER
Preheat your oven to 350°F (175°C). Grease and line an 8x8-inch baking pan (or similar size) with parchment paper for easy removal.
In a medium bowl, whisk together the flour, pumpkin spice, cinnamon, baking soda, baking powder, and salt. Set aside.
In a large bowl, whisk the granulated sugar, brown sugar, and eggs until smooth. Add the oil, pumpkin puree, and vanilla extract, and whisk until fully combined.
Gently fold the dry ingredients into the wet mixture using a spatula, mixing just until no streaks of flour remain. Do not overmix.
MAKE THE CRUMB TOPPING
In a medium bowl, stir together the brown sugar, flour, cinnamon, and salt.
Pour in the melted butter and mix until the mixture looks almost like a dough that can be pressed together and broken into crumbs.
ASSEMBLE & BAKE
Spread half of the pumpkin batter evenly into the prepared pan.
Sprinkle half of the crumb mixture over the top.
Add the rest of the pumpkin batter, smoothing it out gently.
Finish with the remaining crumb mixture sprinkled evenly across the surface.
Bake for 35 to 40 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs.
Let the coffee cake cool in the pan for at least 20 minutes before slicing.