Peel and slice the apples and then toss them into your baking dish. Pour lemon juice over the apples and use your hands mix the apples around to make sure they each get a little juice.
In a small bowl, combine sugar, cinnamon, cornstarch and flour. Sprinkle sugar mixture evenly over your apples. Next, evenly pour 1/2 cup water over your apples.
In a separate bowl, mix all of your topping ingredients. Sprinkle topping evenly over the apples.
Place in the oven and bake for 45 minutes at 350 degrees.
Remove from oven and let cool. Serve with vanilla ice cream.