Preheat oven to 425°F. Place a large baking sheet covered in foil on the lowest rack in the oven to catch drips.

In a large bowl, combine the peaches and lemon juice, then add the rest of the filling ingredients. Stir to coat and pour into a 9x13 baking dish.

Bake the peach mixture in the preheated oven for 10 minutes.

While the peaches are baking, combine the dry topping ingredients and whisk to combine. Toss the grated butter into the flour mixture. Stir in boiling water just until combined.

Remove the peaches from the oven and drop the topping over them in spoonfuls. Sprinkle with the cinnamon sugar topping.

Bake until the crust is golden and a toothpick inserted into the crust comes out clean, about 28 minutes. Serve warm or at room temperature.

The peach filling can be prepared and frozen in advance. Combine the peach filling ingredients in a large ziploc bag, press the air out and freeze flat.

When ready to bake, thaw in the refrigerator, then pour into the baking dish and proceed with the recipe.