Preheat oven to 425°F (220°C). Place a large baking sheet covered in foil on the lowest rack in the oven.
In a large bowl, combine the peaches and lemon juice, then add remaining filling ingredients. Stir to coat and pour into a 9x13 inch baking dish.
Bake the peach mixture for 10 minutes. While baking, combine the dry topping ingredients and whisk. Toss in the grated butter and then stir in the boiling water until just combined, leaving lumps.
Remove peaches from oven and drop spoonfuls of topping over them. Sprinkle with cinnamon sugar topping. Bake until golden and a toothpick inserted into the crust comes out clean, about 28 minutes. Serve warm.
Notes
Serve warm with a scoop of vanilla ice cream for the ultimate Southern treat!