1. In a large bowl, whisk the ricotta with the buttermilk, butter, lemon juice, lemon zest, vanilla extract and egg yolks to combine.
2. In a small bowl, combine the flours, baking powder, salt and nutmeg.
3. In the bowl of an electric mixer fitted with the whisk attachment, whip the egg whites until frothy, about 1 minute. Add the sugar gradually and continue to whisk until soft peaks form, approximately 4 minutes.
4. In a large bowl, mix the ricotta mixture into the flour mixture to combine. Gently fold in the egg whites, mixing just to combine.
5. Heat a griddle over medium heat. Ladle the batter onto the griddle and cook until golden on each side, 3 to 4 minutes per side. Serve immediately.