Preheat oven to 375 degrees. Pour melted butter into center of 9x13 inch baking dish, do not spread butter around pan.
In a separate bowl, combine flour, 1 cup sugar, salt and baking powder. Slowly pour in milk and vanilla extract, and stir to combine.
Pour batter over butter, but do not stir.
Add brown sugar, peach slices, and lemon juice to a saucepan on high heat. Stir frequently until sugar is completely melted and peaches have released their juices.
Pour peaches over top of batter. Do not stir. Bake for 40-45 minutes or until top of cobbler is a golden in color.
Serve Warm or cold, or with a scoop of ice cream.