Preheat the oven to 375 degrees F.
Put the apples on a flat surface. Cut the cheeks from the apple, to remove the core. Cut into fairly thin, but not too thin, slices. Put them in a bowl and add the lemon zest and juice and the orange zest and juice. Toss to coat the apples, then add the molasses, 1/2 teaspoon salt, the cinnamon, ginger, and the nutmeg. Toss to blend.
In another bowl, combine the flour, brown sugar and remaining 3/4 teaspoon salt. Add the butter to the bowl and break it up with your fingers integrating the flour with the butter. Spread it out on a plate or small baking sheet and refrigerate until ready to use.
Butter the bottom and sides of a shallow rectangular baking dish (approximately 13 inches long and 9 inches wide) with the remaining tablespoon of butter. Add the apples and top with the butter-flour mixture. Put the dish in the center of the oven and bake until the apples are tender when pierced with the tip of a knife. The topping should be golden brown as well, about 35 to 45 minutes. Remove from the oven and set aside to cool a few minutes before serving. To serve, garnish with additional lemon zest and ice cream, if desired.
NotesI would love to take full credit for this recipe but it is simply the recipe my mother made year after year when I was growing up. So simple and delicious.
I love all apples but my newest favorites are Braeburn and Rome varieties. They are tart and hold up well when cooked. For this recipe, however, I use pure Granny Smith. Tart, tried and true.