Preheat oven to 425°F. Place a large baking sheet covered in foil on the lowest rack in the oven. This prevents messes from overflow.

In a large bowl, combine peaches and lemon juice, then add sugar, brown sugar, cinnamon, nutmeg, and cornstarch. Stir to coat the peaches and pour into a baking dish.

Bake the peaches for 10 minutes while preparing the topping. In a separate bowl, whisk together flour, sugars, baking powder, salt, and cinnamon. Toss grated butter into the flour mixture. Stir in boiling water until just combined, leaving lumps.

Remove baked peaches from oven and drop topping by spoonfuls over the filling. Sprinkle with additional cinnamon sugar if desired. Bake until golden, about 28 minutes.

Optional: For freezing, prepare filling, freeze in a flat layer in a ziplock bag, and thaw before baking later.