Preheat oven to 425°F (220°C).
In a large saucepan, combine peaches, sugars, cinnamon, nutmeg, lemon juice, and cornstarch. Bring to a boil and simmer until thickened, about 10 minutes.
Pour peach mixture into a 2-quart baking dish.
In a large bowl, mix flour, sugars, baking powder, and salt. Cut in butter until mixture resembles coarse crumbs.
Stir in boiling water just until combined. Drop spoonfuls of dough over the peaches.
Mix the remaining cinnamon and sugar, and sprinkle over the topping.
Bake for 30 minutes or until topping is golden and cooked through.