Preheat the oven to 400 degrees F.
Put the butter in a large ovenproof skillet (10 inches) and place in the oven.
Meanwhile, combine flour, milk, sugar, vanilla, nutmeg, and salt until uniform using a blender.
Remove the hot skillet from the oven.
Swirl the butter around the pan to coat completely, and transfer the remaining butter into the blender. Pulse to blend.
Pour the batter into the skillet and cook for about 20 minutes or until the pancake is puffed.