Preheat oven to 425 degrees F. As oven preheats, place the butter in a 9x13 baking dish and put in oven for the butter to melt.
Place the eggs, milk, flour, salt and vanilla in a blender; cover and process until smooth.
Pour batter into the baking dish with the melted butter. Bake for 20 minutes or until golden brown and puffy.
Remove from oven and sprinkle generously with syrup and powdered sugar or fresh lemon juice and powdered sugar.
