Preheat oven to 400 degrees.
For the dough, mix the flour, sugar, baking powder, salt, and cinnamon in a large mixing bowl. Cut in the butter until you have a coarse, crumbly mixture. Pour in the boiling water and stir together well so that all of the dough is wet. Set aside.
To make the filling, dissolve the cornstarch in the water. Add the berries to a large, deep cast iron skillet over medium heat. Add the cornstarch slurry, lemon juice, and sugar to the pan and stir well.
Heat mixture over medium heat until boiling, stirring frequently. Remove from heat.
Drop pieces of dough over the berry mixture and place the cast iron pan on a foil lined cookie sheet and place in the oven. Bake for 20-25 minutes, until the dough is golden brown and the berries are thick and bubbly.
(If you don't have a cast iron pan, bring to a boil in a sauce pan and bake in a 9x9 baking dish.)
Serve hot with vanilla ice cream.