Step 1: Preheat your oven and skillet. Place a 10-inch cast iron skillet (or an oven-safe heavy-bottomed pan) into a cold oven. Preheat the oven to 425°F (220°C).
Step 2: Prepare the batter. In a blender, combine the eggs, milk, all-purpose flour, granulated sugar, vanilla extract, and a pinch of salt. Blend on high speed until the batter is completely smooth and airy, about 30-60 seconds. You want to see tiny bubbles forming on the surface.
Step 3: Melt the butter. Carefully remove the screaming hot skillet from the oven using oven mitts. Add the unsalted butter to the hot skillet. Swirl the butter around until it's completely melted and coats the bottom and sides of the pan.
Step 4: Pour the batter. Immediately pour the smooth batter into the hot, buttered skillet.
Step 5: Bake to puffy perfection. Return the skillet to the preheated oven. Bake for 15-20 minutes, or until the dutch baby is dramatically puffed up around the edges, golden brown, and slightly crispy. The center should still be a bit custardy. Do not open the oven door during baking.
Step 6: Serve immediately. As soon as you pull the dutch baby from the oven, it will begin to deflate. Dust generously with powdered sugar, a squeeze of fresh lemon juice, and your favorite fresh fruit or maple syrup. Serve and enjoy right away!