
Gather all ingredients and preheat the oven to 375°F (190°C). Lightly grease an 8x8-inch (2 quarts, 20x20 cm) baking dish.
In a saucepan, combine peaches, sugar, cinnamon, and water. Bring to a simmer over medium heat and cook for 12-15 minutes, stirring occasionally, until peaches are softened and liquid has reduced into a light syrup. Remove from heat and rest for 5 minutes.
While the peaches cook, melt ½ cup butter and pour it directly into the prepared baking dish. Tilt the dish to coat the bottom evenly.
In a medium mixing bowl, whisk together flour, sugar, baking powder, and salt.
Add 1¼ cups milk and stir until a smooth batter forms. The batter should be thick but still pourable and should slowly ribbon off a spoon. If it feels too thick, add a small splash of more milk until it reaches that consistency. Let the batter rest for 3 to 5 minutes so the flour can hydrate.
Pour the batter evenly over the melted butter in the baking dish. Do not stir.
Spoon peach mixture evenly over batter. Drizzle the reduced syrup over the top.
Bake for 45-55 minutes, or until the top is golden brown, the center is set, and the edges are bubbling. If the top begins browning too quickly, loosely tent with foil during the final 10-15 minutes of baking.
Remove from the oven and allow the cobbler to cool for 10-15 minutes before serving so it can fully set.