Preheat your oven to 350 degrees Fahrenheit.
Spray a 24 compartment mini muffin tin or 12 compartment regular muffin tin with non-stick cooking spray.
In a large mixing bowl, whisk together the cornmeal, masa harina, granulated sugar, baking powder, baking soda, salt, and cinnamon.
Set aside the bowl of dry ingredients.
In a medium mixing bowl, add the melted butter, pumpkin, buttermilk, sour cream, and egg.
Whisk the wet ingredients together until well blended.
Stir the bowl filled with wet ingredients into the bowl of dry ingredients.
Continue whisking the bater until smooth and creamy.
Fill the muffin tray with the pumpkin cornbread batter.
Bake the muffins for 20 to 25 minutes, or until they start to turn golden brown on top. Test with a toothpick to make sure the batter is cooked.
Remove the pumpkin spice cornbread muffins from the oven, place on a wire rack, and let cool slightly before serving.
If desired, prior to serving, use the wire mesh sieve to dust the top of the muffins with confectioner's sugar.