Preheat the oven to 350 F. Sift the flour with the baking powder and salt. In a medium bowl, using a rotary beater, beat the egg whites until stiff. Gradually add 3 tbsp of sugar and continue beating until stiff peaks form. In a small bowl, beat in the milk and egg yolks into the flour mixture until smooth. Using a spatula or whisk, gently fold in the egg whites and lemon juice until well combined. Heat a large skillet over low heat, transfer the batter to the skillet, spreading it evenly. Decorate the top with apple slices. Sprinkle with the sugar and cinnamon mixture. Cook for about 10 minutes or until the top is glazed.
Serve warm, cut into wedges.