Preheat oven to 400 degrees F. For topping, in a medium bowl stir together flour, the 2 tablespoons sugar, baking powder, salt, and cinnamon. Using a pastry blender, cut in butter until mixture resembles coarse crumbs; set aside.
For filling, in a large saucepan combine the peaches, sugar, water, and cornstarch. Cook over medium heat and stir until slightly thickened and bubbly. Keep filling hot over low heat.