Preheat oven to 375° F. Butter a 9 x 13 baking dish.
Peel and core apples, and cut into thin wedges. Place in large bowl.
In a small bowl, add melted butter and flour and stir to combine.
Add lemon juice, milk and vanilla to the flour mixture; stir to combine; stir in cinnamon, brown sugar and salt. Pour mixture over the apples and fold in until apples are coated. Transfer apples to baking dish.
In the bowl of a food processor, add the flour, brown sugar, oatmeal, salt, baking powder and cinnamon. Pulse a few times to combine.
Add butter to the topping mix and pulse until mixture resembles crumbs. No chunks of butter should remain. If mixing by hand, use a pastry blender or a fork and work the mixture until the butter has combined with the rest of ingredients until the size of small peas.
Sprinkle the topping evenly over the apples in the baking dish.
Place dish on a baking sheet on the center rack of 375° oven for 1 hour.
Apple Crisp is done when the top is golden brown and bubbling.
Serve warm with whipped cream and enjoy.