Preheat oven to 400°F. Place rack on the lowest shelf as the pancake will rise quite a bit. Whisk together eggs, milk, flour, sugar, and salt in a large bowl.
Place butter in a 10-12 inch cast iron skillet, and place pan in the oven to melt the butter. Once butter is melted, remove the pan from the oven, and place whisked egg mixture in the hot skillet.
Carefully transfer the hot skillet back to the 400°F oven, and bake for 20 minutes or until pancake is golden and puffed.
Sift powered sugar over the top of the pancake and serve immediately. Don’t worry as it deflates - it’s supposed to do that.
