In a large bowl, mix the melted vegan buttery spread, the brown sugar, and the organic cane sugar.
Stir in the pumpkin puree, vanilla extract, vinegar, and water.
Add the dry ingredients, and stir well. The batter will be thick. If it seems too dry or lumpy, add a little more water.
Put the batter in the prepared pan and smooth it out.
Make the streusel: place the sugar, gluten free flour, and vegan buttery spread in a bowl. Mix with a pastry cutter until large crumbs form.
Sprinkle the streusel over the cake batter.
Bake at 350 degrees F for 28-32 minutes, or until a toothpick inserted into the middle of the cake comes out clean. Allow the cake to cool before slicing and serving.
Notes
You can make this cake with regular flour if you don't need to be gluten free.Store leftover cake in an airtight container. It does not need to be refrigerated.If you'd like to freeze this cake, allow the cake to cool completely, then wrap the cake in waxed paper or foil and place in a freezer safe bag. The cake should stay fresh in the freezer for 3 months.