Heat butter in a 9- or 10-inch (23 or 25 cm) heavy nonstick oven proof skillet over medium-high heat. Transfer 2 tbsp (30 ml) melted butter to a food processor or blender, leaving remaining butter in skillet.
Add apples, cinnamon and brown sugar to skillet and cook for 10 minutes, or until apples are tender.
Meanwhile, add eggs, granulated sugar, milk and flour to food processor. Blend until smooth. Pour over apples in hot skillet.
Bake in a preheated 425°F (220°C) oven for 20 to 25 minutes, or until browned and puffed.
Shake pan to loosen apple puff pancake. Invert onto a serving platter and dust with icing sugar.