Combine 1/2 cup sugar and 1 tablespoon butter in a medium mixing bowl; beat well.
Combine flour, baking powder, and salt; mix well. Add flour mixture to sugar mixture, and mix well. Stir in milk until dry ingredients are moistened. Spread mixture evenly in bottom of a greased 10- x 6- x 2- inch baking dish. Cover dough with berries; sprinkle with remaining sugar. Dot with remaining butter. Pour boiling water over berries. Bake at 350° for 1 hour.
Note: If substituting frozen berries for fresh, thaw and drain berries, reserving juice. Combine juice and water to yield 1 cup; bring mixture to a boil. Substitute mixture for 1 cup boiling water.