Begin by preheating your oven to 350 degrees F. Spray an 18 x 13 x 1-inch baking sheet with baking spray. Set aside.
In a large bowl, whisk together the flour, cream of tartar, cinnamon, nutmeg, cloves, ginger, baking powder, baking soda, and salt. Set aside.
In the bowl of a stand mixer, beat together the butter and sugar for about 5 minutes or until fluffy. Then, beat in the eggs one at a time, followed by the pumpkin and vanilla extract. Slowly add the dry ingredients to the wet ones and beat until just combined.
Press the dough into the bottom of your prepared baking sheet. Dust your hands with flour if the dough is sticky.
Bake for 15-18 minutes or until a toothpick comes out almost clean. Do not overbake.
While the baked cookie dough cools, prepare your buttercream frosting. In the bowl of a stand mixer, beat the butter for about 1-2 minutes. Slowly add the confectioners' sugar one cup at a time, adding a splash of milk as needed to keep the frosting smooth. Finally, add the pure maple syrup, maple flavoring, salt, cinnamon, nutmeg, and ginger. Mix to evenly combine.
Spread the buttercream frosting over the cooled bars then sprinkle with a light dusting of cinnamon sugar. Slice into desired size and shape.