Preheat oven to 350 degrees F.
Put the butter in a 3-quart baking dish and place in oven to melt.
Mix remaining 1 cup sugar, flour, and milk slowly to prevent clumping. Pour mixture over melted butter. Do not stir.
Warm peaches with syrup in the microwave for about 45 sec – 1min.
Spoon peaches/syrup on top, gently pouring in only 3/4 of the syrup.
Sprinkle top with ground cinnamon, if using. Batter will rise to top during baking.
Bake for 30 to 45 minutes.
To serve, scoop onto a plate and serve with your choice of whipped cream or vanilla ice cream