Preheat your oven to 350°F (175°C). This ensures that the cobbler bakes evenly and the topping becomes golden brown.

In a large mixing bowl, combine the sliced peaches, granulated sugar, flour, cinnamon (if using), and lemon juice. Stir gently until the peaches are well coated. The sugar will help draw out the juices from the peaches, creating a delicious syrup.

Pour the peach mixture into a greased 9x13 inch baking dish, spreading it evenly across the bottom.

In another mixing bowl, whisk together the flour, baking powder, salt, and sugar. This helps to evenly distribute the leavening agent and ensure a light topping.

Add the cold, cubed butter to the flour mixture. Using a pastry cutter or your fingers, work the butter into the flour until the mixture resembles coarse crumbs. This step is crucial for a flaky texture in the topping.

Pour in the milk and vanilla extract, stirring gently until just combined. Be careful not to overmix, as this can lead to a dense topping.

Spoon the batter over the peach filling, spreading it out as evenly as possible. The batter will spread while baking, so it doesn't need to cover every inch.

Place the baking dish in the preheated oven and bake for 35-40 minutes, or until the topping is golden brown and a toothpick inserted into the topping comes out clean.

Once baked, remove the cobbler from the oven and let it cool for about 10-15 minutes before serving. This allows the juices to settle and makes it easier to serve.

Serve warm, optionally topped with a scoop of vanilla ice cream or whipped cream for an extra treat!