Peel and dice apples. In a large bowl, combine diced apples with lemon juice, sugars, cinnamon and flour. Pour into a 2qt baking dish.
In a separate bowl, combine topping ingredients. Use hands to combine butter until crumbly (don't rush this part...it's worth taking the time to be sure everything is combined). Sprinkle over apple mixture. Press lightly.
Bake in 375 degree oven for 45-50 minutes, until bubbly and caramelized. Serve warm with a scoop of ice cream