Preheat the oven to 325 degrees.
Stir the cake mix, pudding mix, rum, eggs, milk, and oil until well blended in a large bowl.
Pour the batter over nuts into a greased pan.
Place into the preheated oven and bake it for 40 to 45 minutes.
For the syrup, stir the butter, light rum, sugar, and water in a saucepan. And then, boil it in low heat for 2 minutes.
Remove the cake from oven and use a long wooden skewer to poke holes in the cake.
Slowly and spoon hot syrup over the cake.
Let the cake cool on the wire rack about 30 minutes.
Slice to serve after cool completely.