Preheat oven to 425°F with the 10" Cast Iron Skillet inside.
Beat the eggs and mix in the flour. Warm the milk separately (cold milk will affect the texture of the finished dutch baby) and mix with the egg and flour mixture. Add sugar, salt, and vanilla and mix well. Batter should be runny.
Once the oven is fully preheated and the skillet is hot, add the butter to the pan. Allow it to melt and gently tilt the pan to coat it. (this will not take long, at this point you should move fairly quickly to avoid burning the butter)
Add the batter to your pan and bake for ~13 minutes. The pancake should have ‘poofed’ up the sides, and appear fluffy, with browning around the edges.
Remove from the oven and top with lemon juice and powdered sugar to taste.
Notes
This could also be made with another oven-safe pot or pan, however I believe that the thick walls of the cast iron skillet give this the best quality even baking.
The pancake will sometimes poof quite a lot while baking (almost like a souffle), it will flatten into a delicious pancake almost immediately upon removing it from the oven.
If you are making a slightly large pancake in a 12″ cast-iron skillet, I recommend increasing this recipe by 50% (multiply all ingredients by 1.5) and using the same baking time/temperature.
[EDIT] We found that the high temperatures of the original recipe were stressing out the seasoning on our cast iron, so we tweaked the cooking time and temperatures above. The original is: 475°F for ~12 minutes