Start by placing the butter in a 9×13-inch baking dish and letting it melt in the oven as it preheats to 350°F.
In a mixing bowl, combine flour, ½ cup sugar, baking powder, salt, and milk. Stir until smooth — don’t overmix.
Drain the canned peaches just enough so they’re not swimming in syrup. In a bowl, toss them with the remaining ½ cup sugar and cinnamon.
Pour the batter over the melted butter in the baking dish.
Don’t stir! Just spoon the peaches and their juice evenly on top.
Slide the dish into the oven and bake for 40–45 minutes, or until the cobbler is golden brown and bubbly around the edges.
Let the cobbler cool slightly before serving.
