Add the apples, cranberries, maple syrup, brown sugar, water, lemon juice, corn starch, and cinnamon to a large mixing bowl. Mix until evenly combined.
Transfer to a 9 or 10" cast iron skillet or 9x13” baking dish.
Bake on the center rack of the oven uncovered for 30 minutes.
Meanwhile, stir together all of the dry ingredients for the topping. Add in wet ingredients and stir until well combined.
After 30 minutes, remove the crisp from the oven, stir, and top evenly with crumble topping. Return to the oven and bake for another 25-30 minutes or until the topping is lightly browned and crispy.
Remove from the oven and let cool for a few minutes before serving.