Whisk flour, sugar, baking powder and salt in a medium bowl until well combined. Set aside. In a separate large bowl, whisk together ricotta, egg yolks, milk, lemon zest and vanilla. Stir flour mixture into egg mixture just until combined.Beat egg whites with an electric mixer at high speed until soft peaks form. Gently fold beaten egg whites into pancake mixture just until blended.Lightly grease a large nonstick griddle or skillet over medium heat.
Pour heaping 1/4 cup batter onto griddle and spread to make about 4-inch pancake. Drop about 10 blueberries onto each pancake. Cook 3 minutes, or until edges are dry and bottom is golden. Flip pancake and cook 2 to 3 minutes longer or until lightly golden on both sides. Adjust heat as needed to prevent burning.
Place pancakes on a heatproof platter and keep warm in oven. Repeat with remaining batter and blueberries.
