Preheat your oven to 350°F. This gives the oven time to reach the proper temperature while you prepare the filling and batter. Have a 9x13 inch baking dish ready.

In a large saucepan, combine the sliced peaches, water, brown sugar, and cornstarch over medium heat. Stir frequently until the mixture thickens and simmers, about 5-7 minutes—the cornstarch will create a glossy sauce that binds the filling together. Remove from heat and stir in the lemon juice, butter, and vanilla extract. The acid from the lemon juice brightens the peach flavor and prevents the filling from tasting one-dimensionally sweet. Pour the warm filling into your prepared baking dish.

In a medium bowl, whisk together the gluten-free flour, sugar, baking powder, and salt. In a separate small bowl, combine the room-temperature milk with the melted and cooled butter—room temperature milk helps the batter mix smoothly without lumps. Pour the wet ingredients into the dry ingredients and stir until just combined; the batter will be thick and slightly lumpy, which is exactly what you want for a cobbler topping.

Spread the batter from Step 3 evenly over the warm peach filling, using a spatula or the back of a spoon to gently distribute it. I like to leave some of the filling visible around the edges—this creates a rustic look and lets those peaches caramelize slightly during baking. In a small bowl, combine the sugar, freshly grated nutmeg, and cinnamon, then sprinkle this mixture generously over the batter.

Place the cobbler in your preheated 350°F oven and bake for 25-30 minutes, until the topping is golden brown and a toothpick inserted into the batter comes out clean. The batter should puff slightly and develop a light golden crust—don't underbake or the topping will be gummy.

Remove the cobbler from the oven and let it cool for at least 20-30 minutes before serving. This cooling time allows the filling to set slightly so it won't run all over the plate, and it brings the temperature to a comfortable eating level. Serve warm with whipped cream or vanilla ice cream if desired.