Preheat the oven to 375°F and lightly butter a 9x13-inch baking dish.
Combine the apples, granulated sugar, brown sugar, flour, lemon juice, vanilla, cinnamon, ginger, and salt in a large bowl. Toss until the apples are evenly coated, then spread them into the prepared baking dish.
12 to 14 cups peeled, cored and sliced tart apples, 2 tablespoons packed brown sugar, 2 tablespoons all-purpose flour, 1 tablespoon lemon juice, 2 teaspoons vanilla extract, 1½ teaspoons ground cinnamon, ¼ teaspoon ground ginger, ¼ teaspoon kosher salt
Mix the flour, brown sugar, oats, cinnamon, nutmeg, and salt in a separate bowl.
1 cup all-purpose flour, 1 cup packed brown sugar, ¾ cup old-fashioned rolled oats, ½ teaspoon ground cinnamon, ¼ teaspoon freshly grated nutmeg, ½ teaspoon kosher salt, ½ cup granulated sugar
Cut the cold butter into the dry ingredients with a pastry cutter or your fingertips until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining. Stir in the chopped nuts, if using.
½ cup cold unsalted butter, Optional: ½ cup chopped pecans or walnuts
Sprinkle the topping evenly over the apples without pressing it down.
Bake for 50 to 60 minutes, or until the topping is golden brown and the apple filling is bubbling around the edges.
Cool for 15 minutes before serving. Serve warm on its own or topped with vanilla ice cream.
Vanilla ice cream