Melt 2 tablespoons of butter in a large skillet over medium-high heat.
Add the apples, cinnamon, 2 tablespoons of sugar, 1/2 teaspoon of lemon zest, and a pinch of salt to the skillet.
Cook the apples, stirring occasionally, until they are tender and golden, then remove from the heat and keep them warm.
Whisk the flour, baking powder, 1/2 teaspoon of salt, and the remaining 2 tablespoons of sugar together in a large mixing bowl.
In a separate bowl, whisk the milk, egg yolks, ricotta, and the remaining 3/4 teaspoon of lemon zest until smooth.
Pour the wet ingredients into the dry ingredients and stir until just combined.
Beat the egg whites in a clean bowl until they hold stiff peaks, then gently fold them into the batter.
Heat a lightly buttered griddle or nonstick pan over medium-high heat.
Drop 1/4-cup portions of batter onto the griddle and cook until bubbles form on the surface.
Flip the pancakes and cook until the other side is golden brown and the center is set.
Serve the pancakes warm, topped with the caramelized apples and a drizzle of maple syrup.