Preheat the oven to 425ºF.
In a 9X13 inch baking dish place the butter and put in the oven while it heats up. This should melt the butter. Remove when it is heated or when the butter has melted. Watch so it does not burn
In a blender combine the flour, milk, sugar, nutmeg and eggs. Blend until smooth, this should take about 2 minutes. If you don't have a blender, you can also use a mixing bowl with a stand mixer, hand mixer or whisked by hand.
Pour into the baking dish with the melted butter and bake for 20 minutes, until the pancake is puffy and golden. Lower the oven temperature to 300 degrees and bake for 5 minutes longer.
Remove from the oven and cut into the pancake. Serve with powdered sugar, berries or syrup.