Preheat oven to 350°F. Coat a 12-in x 17-in bar baking pan with non-stick spray.
In a large mixing bowl, beat fudge mix, butter, brown sugar and cinnamon on high speed for 1 minute. Scrap down sides of mixing bowl. Add eggs, and continue mixing on medium speed for 2 minutes or until combined.
Add flour to batter and beat on low speed for 1 minute or until just combined. Do not over mix.
Spread batter in prepared pan and sprinkle pecans over top. Bake 24-26 minutes or until lightly browned and knife inserted in center comes out clean. Cool completely, and sprinkle with powdered sugar, if desired.