In a large mixing bowl, combine granulated sugar and fresh orange zest. Rub zest into sugar using fingertips for 60 seconds until fragrant and moist.
Add all-purpose flour, baking powder, baking soda, and fine sea salt to the bowl. Whisk for 30 seconds until leaveners are evenly distributed.
In a separate measuring jug, whisk together cultured buttermilk, eggs, melted cooled butter, and vanilla extract until smooth.
Pour wet ingredients into dry ingredients. Gently fold with a spatula just until combined and flour streaks disappear (do not overmix; small lumps are fine).
Gently fold in the roughly chopped cranberries. Allow pancake batter to rest on counter for 10 minutes.
Heat a heavy cast-iron skillet or non-stick griddle over medium heat (350°F/177°C) and lightly brush with butter.
Scoop 1/3-cup portions of batter onto hot griddle. Cook for 2-3 minutes until bubbles form across surface and edges look set.
Flip carefully and cook for 1.5-2 minutes on second side until puffed and golden brown.
Serve hot in tall stacks topped with whipped butter, warm maple syrup, and orange slices.