Preheat oven to 350 degrees. Line a 12 cup muffin tin with liners.
Add the flour, pumpkin spice, baking powder, baking soda, and salt to a small mixing bowl and whisk to combine. Set aside.
Add the pumpkin, brown sugar, vegetable oil, and eggs to a large mixing bowl and whisk well to combine.
Add the dry ingredients to the wet and stir until just combined.
Fill the muffin wells ? full with the batter.
Bake for 18-22 minutes or until the tops spring back when touched and a tester comes out clean. Cool completely before frosting.
For the frosting, add all of the ingredients to the bowl of a stand mixer and beat well with the whisk attachment until smooth and creamy.
Pipe or spoon the frosting over the cupcakes.
Store tightly covered in the refrigerator for up to 5 days.