Preheat the oven to 375°F/180℃ and line an 8x8" baking pan with parchment paper.
In a large bowl, combine the melted butter, sugar, flour and baking powder in a bowl. Mix to form a crumbly cookie dough.
Press about 3/4 of this cookie dough into the base (use a glass/measuring cup/your hands) - creating an even layer.
Spread the cherry pie filling on top. Cover by breaking up and sprinkling the remaining cookie dough on top.
Bake 25 minutes - until the topping looks golden at the edges. Let cool.
Once cool, make the glaze by whisking together the milk and powdered sugar. Use a spoon to drizzle this over the bars before slicing and serving.