1. Zest the lemon and set aside. Juice the lemon, then peel, quarter, and core the apples. Slice the segments lengthwise. Drizzle the lemon juice on the apple to prevent browning and mix to combine.
2. Preheat the oven to 350oF. Crack the eggs into a bowl and cream with the sugar using a handheld mixer.
3. Meanwhile, melt the butter over low heat. Let the butter cool slightly so it is not hot. Pour the butter slowly into the egg mixture. Add the lemon zest, flour, cinnamon and vanilla. Stir until combined. Mix in the milk. Fold the apples into the batter.
4. Grease a 9-inch springform pan with butter and lightly dust the sides with flour. Spoon in the batter. Bake on the middle rack for 55 minutes or until golden brown. Let cool to room temperature, (about 1 hour). Sprinkle with confectioners sugar and cinnamon.
Per serving: 325 calories, 11g fat, 6g saturated fat, 100mg cholesterol, 340mg sodium, 51g carbohydrate, 3g fiber, 30g sugar, 6g protein