Preheat oven to 350 degrees.

Line a 9x9 baking pan with foil and spray lightly with cooking spray.

In a large bowl, combine brownie mix, pumpkin, and 1/2 tsp cinnamon until smooth. It will take a few minutes of stirring for the mixture to come together. Don't be alarmed, at first the batter will appear to be too dry. Keep stirring.

Spread batter into prepared 9 x 9 pan and bake for 25-30 minutes until set. Test with a toothpick.

Let brownies cool completely.

In a bowl, cream together frosting ingredients until fluffy.

Spread on brownies cooled brownies. Makes 9 large brownies.