In a large mixing bowl, using a hand mixer or a stand mixer. Beat together the vegan butter, cane sugar and brown sugar for a minute until fully combined.
Then add the pumpkin butter and vanilla. Continue to beat until fully combined.
In a separate mixing bowl, sift together the flour, baking powder, salt and cinnamon.
Begin adding the dry ingredients to the wet, alternating with the non-dairy milk, until everything is fully combined.
Pour 1/2 the batter into a square 9x9 inch baking pan or 9 inch round pan, lined with parchment paper, and smooth it out evenly. Set the remaining half of the batter aside.
Now, make the middle layer. In a large mixing bowl, add all the ingredients. Then using your hands or a fork, start to work the butter into the dry ingredients. Pinch and press until everything is evenly distributed and crumbly.
Pour the crumble on top of the batter. Then top with the remaining cake batter, smoothing out to evenly cover the crumble as best you can.
Now, make the topping. Add all the topping ingredients to a mixing bowl and do the same thing you did with the crumble. Pinch and press the butter into the dry ingredients until you have a nice crumble.
Spread the crumble topping on top of the cake evenly.
Bake for 50-60 minutes or until the you can stick a toothpick in the center and it comes out clean.
While the cake bakes, make the icing. Whisk together all the ingredients.
Once the cake is done, let cool, then drizzle the top with the icing.
Notes
*You can use store bought or homemade pumpkin butter, I used Trader Joe's. This would also be delicious with apple butter.