Put the butter into a microwave safe bowl and place it in the microwave oven on HIGH for 30-45 seconds or until the butter is melted.
Add the eggs, milk, flour, salt and vanilla to the melted butter. Whisk until all of the ingredients are smooth.
Lightly spray the bottom of a pie pan with nonstick cooking spray. Pour the egg mixture into the pie pan.
Bake the pancake for 25 minutes or until it is puffed and golden brown.
Sprinkle powdered sugar over the top of the pancake, if you'd like and cut into triangles. Serve with syrup.