Preheat the oven to 425° F.
In a blender, combine the eggs, flour, milk, salt, and vanilla.
Blend well, and if any bits of flour stick to the side of the pan, scrape them down with a spatula and blend again.
Take a 9x13 glass baking dish and add the butter. Put it into the oven as it preheats, but keep a close eye on it, and pull it out when the butter has melted.
Pour the batter into the hot baking dish and return to the oven for a final time.
Bake for 20-25 minutes, or until the pancake has lifted and has turned golden brown.
Remove from oven, cut, dust with powdered sugar, or serve with pure maple syrup, or with fresh berries.
