Preheat oven to 400 degrees F (200 degrees C). Place butter in an 8x8-inch microwave-safe baking dish.
Heat butter in microwave until melted, 30 seconds to 1 minute.
Whisk flour, sugar, baking powder, and salt together in a bowl; whisk in milk until batter is smooth. Pour batter over butter without stirring. Spoon pie filling evenly over batter.
Bake in the preheated oven until cobbler is golden brown, about 30 minutes.
