Preheat oven to 350°F. Place butter slices in a 9×13 glass baking dish and melt in oven.
Add peaches, ¾ cup sugar, and salt to saucepan. Cook on medium heat until sugar dissolves and juices form.
In a bowl, combine flour, 1 cup sugar, baking powder, and salt. Stir in milk until just combined.
Remove dish with melted butter from oven. Pour batter over butter without stirring.
Spoon peaches and juice over batter. Sprinkle generously with cinnamon.
Bake at 350°F for 38–40 minutes until golden and bubbly.
Serve warm with ice cream or chill for later.
