Preheat the oven to 350° and place the oven rack in the middle position.
Line a 12 cup muffin pan with cupcake liners and give the liners a quick mist of cooking spray. Set aside.
In a large mixing bowl, add the box of spice cake mix, the can of pumpkin puree, and the pumpkin pie spice.
Using a rubber spatula or a hand mixer, mix all the ingredients together until the cake mix is evenly moistened and well combined with the pumpkin puree. The batter will be thick.
Divide the muffin batter between the 12 muffin cups. These muffins don't rise super high, so be sure to fill the muffin cups pretty full.
Bake in a 350° oven for 23 minutes until the muffins have risen slightly and a toothpick inserted comes out clean.
Allow the muffins to sit 5-10 minutes before drizzling with a glaze or icing. *See notes for icing recipe.