Preheat oven to 425°F. Place a 10-inch cast iron skillet in the oven and heat for 10 minutes.
In a medium bowl, whisk together flour, milk, eggs, salt, and sugar. While whisking, slowly pour in melted butter.
When the pan is heated, remove from oven, place the tablespoon of butter in the pan and swirl to coat. Immediately pour in batter and return to oven.
Bake 18-20 minutes or until browned around the edges and puffed.
Sprinkle with powdered sugar before serving with maple syrup.