Preheat oven to 325 F. Grease and lightly flour Christmas tree pan; set aside.
In large mixing bowl, beat butter and sugar until light and fluffy. Add remaining cake ingredients except fruit and nuts. Blend on low speed one minute, scraping bowl often. Beat 3 minutes on medium speed. Fold in fruit and nuts.
Divide batter evenly in half and spoon into prepared pan. Using a spatula, spread batter out to edges of branches and base of tree. (Note: Batter will be lower in the center of the tree.)
Mound batter slightly in the "star". Place pan on baking sheet and bake at 325 F for 50-60 minutes, until toothpick inserted comes out clean.
Cool 10 minutes in pan. Invert onto cooling rack and cool completely. When cool, place cakes back in pan and use a serrated knife to slice off mounded center, so that the tops are flat.
In medium bowl combine powdered sugar and butter. Stir in rum extract and milk. Beat until smooth and spreadable. Spread 2/3 of frosting on cut side of one cake. Place cut side of second cake against frosting to "sandwich" together.
Stand cake upright on serving plate. Use remaining frosting to decorate as desired.
Recipe courtesy of NordicWare.