Preheat the oven to 425°F. Place a 10-inch skillet or a 9×13 pan in the oven to heat.

Add the butter to the hot pan and return it to the oven while you prepare the batter, allowing the butter to fully melt.

In a blender, food processor, or mixing bowl, combine the flour, milk, eggs, vanilla, sugar, and salt. Blend or whisk until smooth.

Carefully remove the hot pan from the oven and swirl the melted butter to coat the bottom. Pour the batter directly into the pan.

Return to the oven and bake for 20–25 minutes, until the pancake is puffed, set, and golden brown around the edges.

Serve immediately. The pancake will deflate as it cools — this is normal.