For the filling: Preheat the oven to 345 degrees F.
Peel, core and slice the apples to 1/4-inch thickness. Combine the apples, lemon zest and juice, brown and granulated sugars, cinnamon, salt, honey, vanilla and butter in a large pot. Cook on medium heat, gently stirring, until the apples are slightly tender, 8 to 10 minutes.
Mix together the cornstarch and apple juice in a small bowl. Pour over the apple filling, stir together and cook until it comes to a boil. Pour the apple mixture into a lightly sprayed 8-cup casserole dish. Set aside.
For the topping: Place the oats, flour, brown sugar, salt and cinnamon in a large bowl. Lightly stir together by hand. Pour in the honey and melted butter. Mix until incorporated. Sprinkle all over the apple filling.
Bake for 45 to 55 minutes or until the topping is golden all over and the filling has begun to bubble around the edges. Serve with chocolate chip ice cream on top if desired.