German (Puffy) Pancakes

2 Tablespoons melted butter
6 eggs
1 cup milk
1 cup flour
¼ teaspoon salt
1 teaspoon vanilla
pinch nutmeg
pinch cinnamon
zest of one lemon (optional)

Preheat oven to 450ºF. Pour melted butter in a 9x13-inch pan. Blend remaining ingredients until smooth, then bake for 18 minutes until puffed.