Preheat oven to 425 degrees. Place butter, cinnamon and sugar in a 9-inch cake pan. Set in the oven while preparing the other ingredients. Core and chop apple and place in baking pan with butter mixture, swirl around and return to oven. On a blender or food processor, mix together eggs and flour, process/blend until smooth. Pour in milk to blender, blending again until smooth.
Remove pan from oven and carefully pour batter into prepared pan. Bake in a preheated oven for 10 mintues or until set and ligthly browned. Serve immediately!