Adapted from The Italian Country Table
1 c plus 3 T all-purpose flour
1 c whole wheat flour
1-1/2 plus 3 T c sugar
3/4 c cold butter, cut into small pieces
pinch of salt
3/4 c milk
2 eggs
1 t vanilla
zest of one lemon
1 T baking powder
2 large Cortland or other New England apples, cored and cut into small pieces
4 egg whites
Preheat oven to 375ºF. Grease and flour a 9-inch springform pan.
In large bowl, rub together 2 c flours, 1-1/2 c sugar, butter, and salt with fingers until crumbly. Remove 1 c and press over the bottom and along the sides of the prepared pan.
Make a well in the remaining flour mixture. Add milk, 2 eggs, vanilla, lemon zest, baking powder, and the remaining 3 T flour. Blend with a whisk without incorporating the flour.
With a wooden spoon, stir in the flour until well blended but still a little lumpy. Fold in the apples, then scrape batter into pan.
In a separate bowl, beat egg whites with an electric mixer until foamy. Add remaining 3 T sugar and beat until whites start to stand in peaks. Spread over batter.
Bake 65-75 minutes, until knife inserted in the middle comes clean. Cool on a wire rack for 30 minutes.
Slip off sides of pan to finish cooling.