Preheat the oven and pan: Place a 10 or 12 inch oven-safe skillet on the middle rack of your oven. Cast iron is ideal, but a metal cake pan or heavy skillet works too. Preheat the oven to 450 F or 230 C. Let the pan heat with the oven so it gets ripping hot.
Make the batter: In a blender, combine the eggs, flour, milk, sugar, vanilla, and salt. Blend until smooth, about 15 to 20 seconds. No blender at hand? Whisk in a bowl until completely lump free. A few minutes of whisking is worth it for a silky texture.
Let it rest briefly: Set the batter aside for 10 minutes while the oven finishes heating. This short rest relaxes the flour and helps the pancake puff nicely. If your eggs and milk were cold, the rest also takes off the chill.
Melt the butter in the hot pan: Carefully remove the hot skillet from the oven and add the butter. It should melt instantly. Swirl to coat the bottom and sides. You want a glossy, buttered surface so the pancake slides up the edges.
Pour and bake: Pour the batter into the center of the pan and return it to the oven right away. Bake for 13 to 15 minutes, until the edges are towering and deeply golden and the center is set but custardy. Try not to open the oven door, since heat and steam are what make it rise.
Serve immediately: The German Pancake will slump as it cools. That is normal. Bring it to the table hot, cut into wedges, and add your favorite toppings. I love lemon and powdered sugar for a bright, simple finish. Berries and a drizzle of maple syrup make it more dessert-like, in a very good way.