Combine boiling water, rum, and baking soda with dates, prunes, and raisins. After 10 minutes, blend into a paste. In a separate bowl, mix flour and sugar, then add melted butter, vanilla, and eggs.
Prepare the caramel sauce. In a saucepan, combine butter, brown sugar, golden syrup, and rum. Heat until butter melts and sugar dissolves. Let it come to a low boil and cook until thickened. Allow the sauce to cool for 10 minutes before drizzling it over the cake.