Preheat the oven. Set your oven to 350°F and lightly grease or line an 8x8-inch baking pan with parchment paper.
In a medium saucepan or microwave-safe bowl, melt together the butter and coconut oil until fully combined. Set aside to cool slightly.
Now, prep the pumpkin. Place your pumpkin purée between a few layers of paper towels and gently wring out the excess moisture. After draining, you need to be left with about 100 grams of pumpkin. I recommend starting with about 200 grams of pumpkin, to yield 100 grams of dried puree.
To the melted butter/oil mixture, add the pumpkin purée, eggs, and vanilla extract and whisk together until smooth and well combined.
To the wet mixture, add your dry ingredients. Stir until a thick, even batter forms.
Next, make the streusel topping. In a separate bowl, mix together the dry streusel ingredients. Then, pour in the melted butter and vanilla extract, and gently stir with a fork until crumbles form. Avoid over-mixing, you want the texture to stay crumbly and rustic.
Pour the cake batter into your prepared baking pan and smooth out the top. Evenly sprinkle the streusel over the batter.
Bake for 25–28 minutes, or until the top is golden and a toothpick inserted into the center comes out mostly clean with just a few moist crumbs.
Add an optional glaze. Once the cake has cooled, whisk together powdered sugar, dairy-free milk, and a pinch of pumpkin pie spice until smooth. Drizzle over the top of the cooled cake.
Slice and serve. Cut into squares, serve warm or at room temp, and enjoy your perfect cozy fall treat.