Preheat oven to 400 degrees. In a large bowl, whisk the eggs until pale in color and frothy.
Add the flour to the eggs and whisk until smooth. Add the milk, salt, and vanilla extract and mix until incorporated; set aside.
Add the butter to a 9" round pan or cast iron skillet and transfer to the oven until the butter melts (about 5 minutes). Remove from the oven and quickly pour batter into hot pan. Carefully return to oven and bake for 15 minutes. Top with homemade whipped cream, unsweetened applesauce, or maple syrup.