Preheat the oven to 425 degrees.
Place the stick of butter in a 9×13 baking dish and put it in the oven to melt while you prepare the batter. Keep an eye on the butter and remove the pan from the oven if it starts to brown, but work quickly so that the pan does not cool.
Beat the eggs, milk, salt, cinnamon, vanilla, and nutmeg until frothy.
Whisk in the flour until well combined.
Pour over the melted butter in the baking dish. Do not stir.
Bake for 25 minutes or until the center is set and the edges are browned.
Slice into 8 pieces and serve with maple syrup, fresh fruit, or powdered sugar.