• Preheat the oven to 350°F. Line a standard cupcake pan with 12 cupcake liners.
• Whisk together the flour, sugar, pumpkin pie spice, baking powder, and salt in a large mixing bowl.
• Add the pumpkin puree, milk, vegetable oil, egg, and vanilla extract. Whisk just until smooth and combined.
• Divide the batter evenly between the cupcake liners, filling each approximately two-thirds full.
• Bake for approximately 20 minutes or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
• Cool the cupcakes in the pan for 5 minutes. Transfer them to a wire rack and cool completely.

Prepare Buttercream

• Meanwhile, prepare the pumpkin for the buttercream. Spread ½ cup pumpkin puree over several layers of paper towels. Blot with additional paper towels until you've removed enough moisture to reduce the pumpkin to approximately ¼ cup.
• Beat the room-temperature butter until pale and creamy.
• Add the powdered sugar and mix on low speed until completely incorporated.
• Add the dried pumpkin puree, vanilla extract, pumpkin pie spice, and salt. Mix until combined.
• Slowly drizzle in the heavy cream while mixing. Scrape down the sides and bottom of the bowl as needed.
• Increase the mixer to medium speed and whip for approximately 3 minutes until the buttercream becomes smooth and creamy.
• Transfer the buttercream to a piping bag.
• Pipe a generous swirl of pumpkin spice buttercream onto each completely cooled cupcake.
• Sprinkle lightly with cinnamon or pumpkin pie spice, if desired.