Preheat the oven to 325 degrees F. Grease a large bundt cake pan and set aside.

Pour the boiling water, 1/2 cup rum, and baking soda over the dates, prunes, and raisins in the bowl of bowl of your stand mixer. Let stand for 10 minutes before pulsing into a paste.

In a large bowl, whisk the flour and 1 1/2 cups sugar together. Add the 1 cup melted butter, vanilla, and eggs, one at a time, mixing thoroughly. Add the date mixture and stir to combine. Pour the batter into the prepared cake pan and bake for 55 to 60 minutes, until a toothpick inserted comes out clean.

Let cool on a wire rack 10 minutes before turning out to cool completely.

Meanwhile, make the caramel sauce. In a medium saucepan, place the remaining 7 tablespoons butter with the remaining 3/4 cup brown sugar, golden syrup, and remaining 1/4 cup rum. Cook over medium heat, stirring, until the butter has melted and the sugar is dissolved. Bring to a low boil ( watching carefully) and cook for 10 to 12 minutes until thickened. Cool for 10 minutes before spooning over cake.

Slice and serve while still a little warm.