Preheat oven to 350°F. Pour melted butter into a 9x13-inch baking dish.
In a bowl, toss sliced apples with 1/2 cup sugar, cinnamon, nutmeg, and lemon juice. Set aside.
In another bowl, whisk together flour, remaining 1/2 cup sugar, baking powder, and salt. Stir in milk until just combined to form a batter.
Pour batter over the melted butter in the baking dish. Do not stir.
Spoon the apple mixture evenly over the batter. Dot with pieces of cold butter.
Bake for 45-50 minutes until golden brown and a toothpick inserted into the crust comes out clean.
Allow to cool for 10-15 minutes before serving warm.