Preheat oven to warm setting, about 180°F.
In a large pot with a lid, or 5-quart Dutch oven, bring water, maple syrup, rum, and 1/2 teaspoon of salt to a boil over medium heat. Once it reaches a boil, reduce it to a simmer.
While the syrup is coming to temperature, start the dumpling dough. Add flour, baking powder, baking soda, and remaining salt to the bowl of a food processor with the blade attachment. Pulse to combine.
Cube the cold butter into 1/2-inch pieces.
Add the cold butter to the food processor.
Pulse 6-8 times, or until it resembles a coarse meal.
Pour the mixture into a larger bowl and add the buttermilk.
Stir until combined. If dry, add another tablespoon of buttermilk.
Use a spoon or small ice cream scoop and drop dough balls into the simmering sauce. Fill the pot 2/3 full. Cover the pot with a lid and reduce heat to low.
Simmer until cooked through, about 10 minutes.
Transfer the cooked dumplings to an oven-safe dish and place in the warm oven.
Repeat with the remaining dough. If the sauce gets too thick, add a little water to thin it out.
Serve the dumplings warm with whipped cream or ice cream and toasted pecans.