Preheat oven to 350F.
Whisk together the all purpose flour, baking powder, pumpkin pie spice, cinnamon, and salt. Set aside.
In a separate bowl, whisk together the melted vegan butter, coconut sugar, and pumpkin purée.
Whisk the aquafaba by hand until light and frothy in a small bowl. Not looking for stiff peaks or anything, just frothy. It will turn white and bubbly. Add the aquafaba to the wet ingredients and use a spatula to combine.
Combine the dry and the wet ingredients and fold until just combined. Don't over mix.
Line an 8x8 baking pan with parchment paper. Pour the batter in the pan and spread evenly. Bake for 35-40 or until you can press down gently on the center of the cake and it bounces back. Allow to cool completely before frosting.
Once cool, make the frosting by combining soften butter and cream cheese to the bowl of a stand mixer. Can also do this with a hand mixer. Whip the cream cheese and butter together and then add in the powdered sugar. Beat on medium-high until light and fluffy.
Frost the pumpkin bars. Cut in to 9-12 bars and serve!