In a pot on medium heat, combine the blueberries, 1 cup sugar, and lemon juice. Let that boil. In a bowl, combine flour, 1 cup sugar, baking powder, salt and butter. Mix it all together using your clean hands until the mixture resembles walnut size pieces. Add the hot water.
Stir together with a spoon until moistened. Set it aside.
Add the cornstarch mixture into the boiling blueberries. Stir until thickened.
Preheat oven to 355°. Line a sheet pan with foil. Put the blueberry mixture into the baking dish.
Spoon the batter on top of the blueberries.
Stick it in the oven to bake for 45 minutes to an hour.
Chill for 5 minutes before serving.
