Pour the melted butter into a 13 by 9 by 2-inch baking dish.
In a medium bowl, combine the flour, 1 cup sugar, the baking powder, and the salt and mix well. Stir in the milk, mixing until just combined. Pour this batter over the butter but do not stir them together.
In a small saucepan, combine the peaches, lemon juice, and remaining cup of sugar and bring to a boil over high heat, stirring constantly. Pour the peaches over the batter but do not stir them together. Sprinkle with cinnamon or nutmeg if desired.
Bake in the preheated oven for 40 to 45 minutes or until the top is golden-brown. Serve warm or cold.