Place egg whites into bowl; beat until stiff peaks form. Set aside.
Combine egg yolks, ricotta cheese, melted butter, sugar and salt in bowl; beat until well mixed. Add flour; mix until just combined. Fold in lemon zest and egg whites until well incorporated.
Heat griddle or large skillet over medium-low heat. Spoon scant ¼ cupfuls batter onto griddle; cook 5 minutes or until deep golden brown. Turn pancakes over; continue cooking 3 minutes or until deep golden brown. Repeat with remaining batter.
Serve immediately with additional butter and powdered sugar, if desired.
