Preheat oven to 350. Place the butter in a 2 quart baking dish and place in oven as it preheats. Place the peaches in a bowl and stir in the 1/2 c. of sugar. Set to the side. In a medium bowl mix flour, sugar, baking powder, salt, milk, and vanilla together. Pour on top of melted butter. Spoon the peaches on top of the batter (I like to sprinkle some cinnamon sugar on top). Bake for 45 minutes or until done.