Preheat your oven to 375°F (190°C) and grease a 9x13-inch baking dish.

In a large mixing bowl, combine all-purpose flour, granulated sugar, baking powder, and salt. Whisk thoroughly.

Cut in chilled unsalted butter until the mixture resembles coarse sand.

Add the egg and milk to the flour mixture and stir until a soft dough forms.

Pat half of the dough into the bottom of the prepared baking dish.

In a separate bowl, toss the cherries with cornstarch and sugar until coated, then spread over the dough.

Crumble the remaining dough over the cherry filling evenly.

Bake for about 35 minutes, until the topping is golden brown and the filling is bubbling.

Cool completely on a wire rack, then slice into squares and serve.