Preheat your oven to 350°F (175°C) and grease a 9-inch square baking pan with butter or line it with parchment paper for easy removal.

In a medium bowl, whisk together 2 cups of all-purpose flour, 2 teaspoons of baking powder, and ½ teaspoon of salt until well combined.

In a large mixing bowl, cream together ½ cup of cold unsalted butter and 1 cup of light brown sugar until fluffy and light in color, about 3-5 minutes.

Gradually add the dry mixture to the creamed butter and sugar, alternating with ½ cup of whole milk.

Pour half of the batter into the prepared pan, layer 3 cups of sliced ripe peaches over it, then spoon the remaining batter on top to cover the peaches.

For the crumble, combine ½ cup of light brown sugar, 1/3 cup of all-purpose flour, and ¼ cup of cold unsalted butter in a small bowl and mix until crumbly.

Sprinkle the crumble topping generously over the batter.

Bake for 40-50 minutes, or until a toothpick inserted in the center comes out clean.

Let the cake cool in the pan for 15-20 minutes before slicing.