In a food processor or blender, combine citrus peel, raisins, mixed dried fruit, prunes, cinnamon, ginger, vanilla extract, nutmeg, dark rum, orange zest, and port. Blend to desired consistency, scraping down the sides as needed.
In a large mixing bowl, prepare the boxed cake mixes according to package instructions. Add Caribbean browning and whisk until well incorporated.
Fold the fruit mixture into the cake batter until evenly distributed.
Preheat oven to 350°F (175°C).
Grease and flour Bundt or cake pans. Divide the batter between the pans. Bake according to package directions, typically 45 minutes, or until a toothpick inserted into the center comes out clean.
Allow cakes to cool in the pans for 10 minutes, then transfer to a cooling rack. Once completely cooled, brush the tops with additional port or rum.
Slice and enjoy. Store any leftovers in an airtight container.