In a small bowl, whisk together flour, baking soda and salt.
In a large bowl, beat together buttermilk, egg yolks, sugar, lemon zest and ricotta cheese by hand.
In a clean bowl, using an electric mixer, beat egg whites until soft peaks form.
Add dry ingredients to buttermilk mixture until just combined; gently fold in egg whites until they are just incorporated.
Coat a large nonstick griddle or pan with cooking spray; heat over medium heat. Spoon batter into pan in batches using a 1/4-cup batter for each pancake; cook until lightly browned, about 2 to 3 minutes per side. Remove pancakes to a tray in a warm oven and repeat with remaining ingredients (being careful not to spray cooking spray into open flame). Yields 2 pancakes per serving.
You can thin the batter out with a little water if desired.