Heat the oven to 400 F. Line a rimmed baking sheet (about 13 by 18 inches) with parchment paper.
Coat the parchment paper and sides of the baking sheet with about 1 tablespoon of the melted butter.
Mix together buttermilk, eggs, vanilla extract, and 4 tablespoons of the melted butter in a large bowl and whisk until combined.
In another bowl, mix together flour, sugar, baking powder, baking soda, and salt.
Slowly whisk the dry ingredients into the wet, and mix until just combined.
Pour the batter into the prepared baking sheet and smooth it into an even layer.
Sprinkle on desired toppings.
Bake until the pancake is lightly golden and springs back when touched, 12 to 15 minutes.
Remove the pancake from the oven and heat the broiler to high. Brush the remaining melted butter onto the pancake. Broil until golden brown, about 2 minutes.
Cut and serve warm with powdered sugar and maple syrup