1. Preheat your oven to 425°F (220°C).
2. Place the butter in a 9×13 baking dish and let it melt in the oven while you mix the batter. Keep an eye on it to prevent browning, but work quickly to avoid cooling the pan.
3. In a bowl, whisk together the eggs, milk, salt, cinnamon, vanilla, and nutmeg until frothy.
4. Gradually add the flour and mix until fully combined.
5. Pour the batter over the melted butter in the baking dish without stirring.
6. Bake for 25 minutes or until the center is firm and the edges are golden brown.
7. Cut into 8 pieces and enjoy with maple syrup, fresh fruit, or powdered sugar.