Preheat oven to 375ºF.
Lightly grease 9×13 inch baking pan.
Add the peaches to the pan.
Sprinkle with cornstarch, cinnamon and nutmeg and toss to combine.
In a bowl combine the flour, sugar, baking powder and salt.
Sprinkle the flour mixture over the peaches.
Sprinkle the brown sugar on top.
Use a cheese grater to grate the butter.
Sprinkle the grated butter over the top of the cake.
Bake in preheated oven for 35-40 minutes or until golden.