Heat oven to 350. Generously spray 12-cup Bundt cake pan with baking spray with flour. Pour 2 tablespoons of the melted butter evenly in bottom of pan. Sprinkle brown sugar over butter. Cut pineapple slices in half. Line bottom of pan with pineapple halves, fitting slices close together. Set aside.
In large bowl, beat cake mix, remaining ¼ cup melted butter, ½ cup reserved pineapple juice, eggs, bananas, cinnamon and nutmeg with electric mixer on medium speed 2 minutes. Pour into pan over pineapple. Bake 40 to 45 minutes or until toothpick inserted in center comes out clean. Remove from oven; cool 15 minutes.
In small bowl, mix filling ingredients. With handle of wooden spoon (¼ to ½ inch in diameter), poke holes halfway down in cake every inch, wiping spoon handle occasionally to prevent sticking. Carefully pour filling mixture over holes in cake, using spoon to direct mixture into holes. Refrigerate in pan uncovered 2 hours.
Remove from refrigerator and run metal spatula around outer and inside edges of pan to loosen cake; turn upside down onto serving platter. In small bowl, mix powdered sugar and 2 teaspoons reserved pineapple juice. Drizzle on top of cake; sprinkle with pecans.
* To toast pecans, sprinkle in ungreased heavy skillet. Cook over medium-low heat 5 to 7 minutes, stirring frequently until golden brown.