tart apple, peeled and thinly sliced
In a small bowl, combine the flour and baking powder. In another small bowl, whisk the egg yolks, milk and lemon juice. Stir into dry ingredients and mix well; set aside.
In a third small bowl, beat egg whites on medium speed until soft peaks form. Gradually beat in the sugar, 1 Tbsp. at a time, on high until stiff peaks form. Fold into yolk mixture.
Pour into a shallow 1-1/2-qt. baking dish coated with cooking spray. Arrange apple slices on top. Combine sugar and cinnamon; sprinkle over apples.
Bake, uncovered, in a preheated 375-degree oven for 18-20 minutes or until a knife inserted near the center comes out clean. Cut in half and serve while warm.