Place a 10-inch cast-iron skillet in the oven and preheat to 425°F (220°C). Let the skillet heat for at least 10 minutes after the oven reaches temperature. A thoroughly heated pan is important for the pancake's rise.

Add the eggs, milk, flour, sugar, vanilla, and salt to a blender. Blend for about 15 to 20 seconds, just until smooth. Alternatively, whisk the eggs and milk together, then gradually whisk in the flour, sugar, vanilla, and salt. The batter should be thin and completely pourable.

Let the batter rest for 5 minutes while the skillet finishes heating. This allows the flour to hydrate and helps reduce excessive bubbling in the batter.

Carefully remove the skillet from the oven using oven mitts. Add the butter and swirl the pan until the butter melts and coats the bottom and lower sides. Work quickly so the skillet remains hot.

Immediately pour the batter into the center of the buttered skillet. Do not stir or spread it. Return the skillet to the oven.

Bake at 425°F (220°C) for about 18 to 20 minutes. The edges should rise dramatically and become deep golden brown, while the center should look puffed and set around the edges but still slightly soft.

The pancake is ready when the edges are crisp and browned and the center no longer looks like liquid batter. If the center is still very wet, bake for another 1 to 2 minutes.

Remove the skillet from the oven and place it on a heatproof surface. Let the pancake rest for about 5 minutes. It will naturally deflate as it cools, leaving a tender center and browned edges.

Dust with powdered sugar and add optional fresh berries, lemon juice, or maple syrup. Cut into wedges and serve immediately.