Preheat oven to 425 degrees F (220 degrees C).

Place butter in a 10 inch cast iron skillet.

Heat the skillet in the oven until butter is melted.

Beat eggs at high speed with an electric mixer.

Slowly add the milk and flour to the eggs, mixing until smooth.

Pour batter into the hot skillet with the melted butter.

Return skillet to oven and bake for 20 minutes, or until puffed and golden brown.

Remove from oven and let cool slightly; it will deflate.

Lightly dust with confectioners' sugar and serve immediately.