In a mixing bowl, combine blackberries, sugar, and lemon juice. Gently toss to coat and set aside.

In a separate bowl, whisk together flour, baking powder, sugar, and salt.

Add milk and melted butter to the dry ingredients, stirring until just combined.

In a saucepan, combine water and sugar. Bring to a simmer.

Drop spoonfuls of the dumpling dough into the simmering water. Cover and cook for 15-20 minutes until dumplings are fluffy.

Remove dumplings and place them in a serving dish. Spoon blackberry filling over the top and drizzle with the sauce.