Preheat your oven to 350°F (175°C). Spray a 9x13-inch baking dish with nonstick spray.

In a medium saucepan over medium heat, combine sliced peaches with granulated sugar, brown sugar, and a pinch of salt. Cook for 3-4 minutes.

Melt the unsalted butter until fully liquefied, pour it into the prepared baking dish without stirring.

In a mixing bowl, sift together flour, granulated sugar, baking powder, and a pinch of salt. Add milk and whisk until smooth. Pour over melted butter.

Spoon the peach mixture over the batter, ensuring even distribution, and drizzle some peach juice across the batter.

Sprinkle brown sugar and cinnamon over the top.

Bake for 38-42 minutes until the top is golden-brown and edges are bubbling.

Let it cool for about 10 minutes before serving warm, preferably with vanilla ice cream or whipped cream.