Toss the berries through salt in a large bowl until well blended. Pile into an unbaked pie shell.
In a medium bowl, mix the flour, brown sugar, cinnamon, and baking powder. Add the melted butter and stir with a fork until crumbs form. Crumble on top of a pie and bake at 425 F for 15 minutes. Lower the oven to 350 F and bake until the fruit is tender, about 40 minutes. If the topping is browning too quickly, tent it with foil.
