In a blender, combine eggs, flour, warm milk (30 seconds in the microwave), sugar, vanilla extract and a pinch of salt. Blend until combined.
Remove the hot pan from the oven. The butter should have melted. Swirl butter around pan to coat entire surface. Pour any remaining butter into the batter and blend. Then pour the batter into the hot pan and return the pan to the oven. Cook until the pancake is puffed in the center and golden brown at the edges. This takes 20-25 minutes.