I think this recipe started out as America's Test Kitchen recipe that has been modified over time. It's delicious - a tasty apple cake with a custard layer, and it's not too sweet. Most recently I barely got to take the picture before my family tore into it! Enjoy. —Leith Devine
Preheat oven to 325 degrees. Spray a springform pan with cooking spray.
Peel and slice the apples into a bowl. Microwave them until softened, about 5-6 minutes, stirring halfway through. When done add Grand Marnier and lemon juice and set aside to cool.
In a small bowl mix 1 cup flour, brown sugar (make sure there are no lumps), 1/4 cup white sugar, baking powder, and salt.
In a large bowl with an electric mixer combine the egg, melted butter, milk, vanilla and 1 tsp of the cinnamon. Add the flour mixture and combine. Remove 1 cup of the batter.
Add the egg yolks to the large bowl and combine. Add the apples. The batter will be thin, don't worry!
Add the 2 TB of flour to the 1 cup of batter you've set aside and whisk to combine.
Put the contents of the large bowl with the apples into the springform pan. Put the remaining 1 cup of batter on top of the apple layer and carefully spread. The top layer is thick but it will spread with a knife or the back of a spoon.
Combine 1 TB sugar and 1/2 tsp. cinnamon and sprinkle over the top.
Bake for 1 hour 15 minutes, a knife. should come out clean when inserted. Dust with powdered sugar. I serve this with whipped cream.