Step #1 In a large bowl, mix flour, baking soda, sugar, & salt.
Step #2 In a medium bowl, egg yolks, whisk buttermilk, & lemon peel to mix.
Step #3 Stir buttermilk mixture into flour mixture just until evenly moistened.
Step #4 Gently stir in the ricotta cheese.
Step #5 In a bowl, with a mixer on high speed, beat the egg whites until soft peaks form.
Step #6 With a flexible spatula, carefully fold the whites into the batter just until they are incorporated.
Step #7 Place a nonstick griddle or a 12-inch nonstick frying pan over med-heat/flame (350°); when hot, coat lightly with oil & adjust heat to maintain temperature.
Step #8 Drop batter in 1/2-c portions onto the griddle & cook this until pancakes are browned on the bottom & edges begin to look dry, about 2 mins; turn cakes with a wide spatula & brown other sides, 1 1/2 to 2 mins longer.
Step #9 Coat pan with more oil as necessary to cook remaining pancakes.
Step #10 Serve pancakes as cooked, or keep warm in a single layer on baking sheets in a 200° oven for up to 15 mins.