Preheat oven to 325 degrees. Grease and flour a 10-inch tube pan and set aside.
Beat butter at medium speed with an electric mixer for 2 minutes. Gradually add sugars, beating well between each addition. Add eggs, one at a time, beating just until the yellow disappears.
In a small bowl, combine milk, rum and vanilla; set aside. In a separate bowl, combine flour, baking powder and salt. Add to butter mixture alternately with milk mixture, beginning and ending with flour mixture. Beat at low speed just until blended after each addition. Fold in pecans.
Pour batter into prepared tube pan. Bake 80 minutes or until a wooden pick inserted in the center comes out clean. Cool pan on a wire rack for 15 minutes. Remove from pan and let cool completely on wire rack.
To make 6 mini-loaf pans instead of one tube pan, decrease cooking time by half; use a cake tester for doneness.