3 tablespoons butter
2 eggs room temperature
1 egg white, room temperature
2/3 cup whole milk at room temperature
2 tablespoons granulated sugar
1/2 cup plus 2 tablespoons flour
1/2 teaspoon vanilla extract
1/4 teaspoon ground cinnamon
a pinch of nutmeg
1/4 teaspoon kosher salt
powdered sugar, cinnamon, and lemon juice for topping as desired.

3 tablespoons butter 2 eggs room temperature 1 egg white, room temperature 2/3 cup whole milk at room temperature 2 tablespoons granulated sugar 1/2 cup plus 2 tablespoons flour 1/2 teaspoon vanilla extract 1/4 teaspoon ground cinnamon 1/4 teaspoon kosher salt

Preheat the oven to 400F. Place the 10" cast iron skillet in the oven and heat for at least 8 minutes.
Melt 3 tablespoons butter in a saucepan or in the microwave.
In a blender, put the eggs, egg white, milk, 1 tablespoon melted butter, sugar, flour, vanilla, nutmeg, cinnamon, and salt. Blend until the batter is smooth and creamy (about 30 seconds). Carefully remove the hot skillet from the oven. Pour the remaining 2 tablespoons melted butter into the pan and swirl to coat the bottom.
Gently pour the batter into the hot skillet (beware of splatter). Return the pan to the oven and bake for 20 minutes. Do not open the door in the meantime or the pastry will fall.
Once the Dutch baby is done baking, remove the skillet from the oven and use a thin spatula to gently coax the pancake onto a large plate. To serve, cut into wedges and sprinkle with cinnamon, powdered sugar, and a splash of lemon juice.
Enjoy