Preheat the oven to 410º F (210° C). Place a 9.85 inches (25 cm) diameter cast iron skillet inside the oven to heat for at least 5 minutes.
Place the eggs with the flour, milk, sugar, salt and vanilla extract in a blender. Blend for a few seconds to obtain a liquid and homogeneous mixture.
Open the oven, add the butter to the pan and close the oven again so that the butter melts but does not burn.
Carefully remove the pan from the oven and add the pancake mixture. Place the pan back in the oven and bake the pancake for 20 minutes until puffed and very golden brown.
Once the pancake is ready, remove it from the oven and decorate it with powdered sugar and red fruits if desired. Serve directly from the pan and with some maple syrup.