In a large bowl, combine the sliced peaches, sugar, lemon juice, vanilla extract, cornstarch, and cinnamon. Mix gently and let it sit while you prepare the topping.
Make the Topping:
In another bowl, whisk together the flour, sugar, baking powder, and salt. Stir in the milk, melted butter, and vanilla extract until just combined.
Assemble:
Pour the peach mixture into a greased 9×13-inch baking dish. Spoon the topping over the peaches. Don’t worry about covering it completely; it will spread as it bakes.
Bake:
Bake for about 35-45 minutes, or until the topping is golden brown and a toothpick inserted in the center comes out clean.
Serve:
Let it cool slightly before serving. It’s delicious on its own or topped with vanilla ice cream!