Preheat oven to 350 degrees and grease a 2 qt baking dish.
Toss the apples with the peanut butter, brown sugar, cornstarch, vanilla, 1 tsp cinnamon, and ¼ tsp salt until well combined. Pour the apple mixture into the greased baking dish.
Make the crumble topping. Stir the flour, oats, brown sugar, baking powder, cinnamon, and salt until well combined. Cut in the cubed butter until the mixture forms crumbs.
Sprinkle the crumble topping evenly over the apples.
Bake for 30-35 minutes, or until golden brown on top. Allow to cool at room temperature for 15 minutes and serve with ice cream.
Notes
*By warming the peanut butter 10-15 seconds in the microwave it makes it much easier to stir into the apple mixture.