Heat butter in a large glass bowl in microwave on high until melted, about 30 seconds. Whisk in confectioners' sugar, rum extract, and water, stirring to form a smooth sauce. Heat jam in a small glass bowl in microwave on high until just melted, about 30 seconds. In six small bowls or wineglasses, evenly distribute pound cake cubes. Pack cubes down slightly. Drizzle rum sauce and jam evenly over each. Spoon 3 tablespoons of pudding evenly over each. Refrigerate for 45 minutes. Garnish with raspberries and serve.