Whisk buttermilk, pumpkin puree, egg yolks, sugar, and vanilla extract together in a bowl until blended. Whisk in melted butter.
Whisk cake flour, pumpkin pie spice, baking soda, baking powder, and salt together in a bowl. Add flour mixture to buttermilk mixture and whisk to combine.
Beat egg whites in a glass or metal bowl until soft peaks form. Lift your beater or whisk straight up: the egg whites will form soft mounds rather than a sharp peak. Fold egg whites into buttermilk-flour mixture to form pancake batter.
Heat a lightly oiled griddle or skillet over medium heat. Drop batter by large spoonfuls onto the griddle and cook until bubbles form on top, 1 to 2 minutes. Flip and cook until browned on the other side, 1 to 2 minutes. Repeat with remaining batter.