Preheat the oven to 350°F (180°C). Line a cupcake tray with 12 muffin liners.
Sift all purpose flour into a mixing bowl and add light brown sugar, white granulated sugar, baking soda, baking powder, salt and pumpkin pie spice.
Prepare your flax egg by mixing 1 Tbsp of ground flax seed meal with 3 Tbsp Hot Water and allowing to sit for a minute to become gloopy.
Add the flax egg, pumpkin purée, oil, vinegar and vanilla to the mixing bowl and mix into a thick batter. Don't overmix.
Divide the batter evenly between the muffin liners in the cupcake tray.
Bake for 25 minutes or until a toothpick inserted into the center of one of the cupcakes comes out clean.
Let the cupcakes cool for a few minutes before transferring them to a wire cooling rack to cool completely before frosting.
Prepare your frosting by adding the vegan butter, powdered sugar, vanilla and soy milk to the bowl of an electric mixer. Start on slow speed and gradually increase the speed until thick and smooth. When you reach the right consistency add in the pumpkin pie spice and mix in on slow until just mixed.
Pipe the frosting onto the cupcakes and decorate with pumpkin pie spice and crushed pecan nuts.