Melt butter in 13 x 9 inch baking dish. Combine flour, 1 C sugar, and baking powder. Add milk, stirring just until moistened. Pour batter over butter...do not stir.
Bring remaining 1 C sugar, peach slices and lemon juice to a boil over high heat, stirring constantly; pour over batter..do not stir. Sprinkle with cinnamon or nutmeg if desired (I did not).
Bake at 375 for 35-45 min or until golden brown.
I did not measure the peaches but used 5 so it was probably a little more than 4 cups.