Preheat the oven to 350°F and line 14 standard muffin cups with cupcake liners.

Whisk together flour, baking powder, salt, and pumpkin spice mix in a medium bowl; set aside.

Beat brown sugar, granulated sugar, and butter in a large bowl with a hand mixer or stand mixer fitted with the paddle attachment until light and fluffy. Add eggs one at a time, beating well after each addition, then add vanilla after the last egg.

Add the pumpkin puree and mix on medium until the mixture is smooth and creamy, about 30 seconds.

Alternately add the flour mixture and buttermilk in three additions of flour and two of buttermilk, beginning and ending with flour. Fold the final flour addition in by hand to avoid overmixing.

Scoop the batter into the prepared tins, filling almost to the top of each cup. Bake 16 to 20 minutes, until a toothpick inserted in the center comes out with a few clinging crumbs. Start checking at 16 minutes.

Remove cupcakes immediately from the muffin tins and cool completely on a wire rack before frosting.

Stir maple syrup and cinnamon into the prepared cream cheese buttercream, then frost cooled cupcakes with your preferred piping tip.