In a food processor or blender, combine the flour, milk, eggs, sugar and cinnamon and blend until smooth. Set aside.
Place butter in a 10-inch cast iron skillet and place in oven. As soon as it is melted, pour batter into the skillet and place back in the oven. Bake for 15-20 minutes until the pancake puffs and becomes golden brown.
Remove from the oven and serve immediately. Top with powdered sugar, syrup and berries.