Put lemon juice, vanilla and maple syrup in a large bowl.
Peel and slice apples and mix with the lemon juice mixture.
Pour into your baking dish (I often use a deep dish pie plate).
In a medium sized bowl, mix brown sugar, cinnamon, flour, oats and butter with your hands until butter is fully mixed in. The butter may resemble the size of peas.
Sprinkle crisp topping on top of apples.
Bake on a cookie sheet in a 375 degree oven for approximately 30 minutes or until apples are soft and bubbling and top has started to brown.
Serve with vanilla ice cream (optional but delicious).