Preheat oven to 425°F. Line a half-size baking sheet (18"x13") with parchment paper. Spray parchment paper and inside rims of the baking sheet with nonstick cooking spray, or brush with additional melted butter. Set aside.
In a large mixing bowl, add dry ingredients (flour, granulated sugar, baking powder, and salt) and whisk well to combine.
In a separate, smaller bowl, add the wet ingredients (buttermilk, eggs, vanilla, and 6 Tbsp of the melted butter), and whisk to combine.
Pour the contents of the wet ingredients bowl into the bowl with the dry ingredients, using a rubber spatula to stir them together gently.
Stir until you no longer see flour streaks, but don't worry about getting all the little lumps out.
Transfer batter to the prepared baking sheet and spread into an even layer. Top with any desired toppings (or leave the pancake plain).
Bake for 13-15 minutes, until golden brown and set in the center.
Remove pancake from the oven, and brush with remaining 2 Tbsp of the melted butter. Return to the oven to bake or broil for another minute or two. This will mimic the buttery golden brown top of a griddled pancake.
Let the pancake rest a minute or two, then slice and serve as desired.