Bars: Preheat oven to 350°F. Lightly butter and flour 9-inch square pan*.
In large bowl, beat together butter and sugar with electric mixer until creamy. Add egg and rum; mix to combine.
In small bowl, whisk together flour, baking soda, baking powder, cinnamon and salt; gradually add to butter mixture. Mix in bananas and pecans; stir to incorporate. Pour batter into prepared pan and spread evenly. Bake for 20 to 25 minutes or until toothpick inserted in the center comes out clean. Remove pan to a wire rack to cool completely.
Frosting: In large bowl, combine butter, cream cheese, sugar and extract with an electric mixer. Beat until light and fluffy. Add cinnamon and 1 cup confectioners' sugar; blend until smooth (careful; over mixing will cause separation). Add additional confectioners' sugar to create desired consistency.
Spread frosting immediately over cooled bars. Cover and store bars in refrigerator for up to 3 days. When ready to serve, cut bars into 2-inch squares. If desired, top each square with a pecan half.
*For a thicker bar, use an 8-inch square pan.