Put berries in pan and sprinkle with lemon juice. Cream butter and gradually blend in 3/4 cup of the sugar. Add milk, flour, baking powder and 1/4 teaspoon salt; beat until well combined. Spread batter over berries. Mix remaining 1 cup sugar, remaining 1/4 teaspoon salt and the cornstarch; sprinkle evenly over batter. Very carefully pour boiling water over all. Bake in 375 degree oven for 50-60 minutes, or until crust is light brown.