Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan or line it with parchment paper.

In a small bowl, whisk together the ground flaxseed and water; let it sit for 5 minutes until thickened to create the flax eggs.

In a large mixing bowl, sift together the flour, baking powder, baking soda, pumpkin pie spice, and salt.

In a separate medium bowl, whisk together the pumpkin puree, cane sugar, brown sugar, melted coconut oil, prepared flax eggs, almond milk, and vanilla extract until smooth.

Gradually pour the wet ingredients into the dry ingredients. Use a spatula to fold the mixture together until just combined, ensuring no flour streaks remain.

Pour the batter into the prepared baking pan and spread it evenly into the corners.

Bake for 28-32 minutes, or until a toothpick inserted into the center comes out clean.

Remove the pan from the oven and allow the bars to cool completely on a wire rack before frosting.

To make the frosting, cream the vegan butter and vegan cream cheese together in a bowl using a hand mixer until smooth. Gradually add the powdered sugar and vanilla, beating until light and fluffy.

Spread the frosting evenly over the cooled pumpkin bars. Refrigerate for 30 minutes to set the frosting before slicing into 24 squares.