1. Preheat your oven to 350 degrees.2. In a medium bowl, mix the apples, cherries, granulated sugar, lemon juice, and 3/4 teaspoon of ground cinnamon and set it aside.
3. In a separate medium bowl, combine the all-purpose flour, rolled oats, one teaspoon of ground cinnamon, and kosher salt. Add the butter and use a manual food chopper to cut it into the mixture.
4. Transfer and evenly spread the fruit mixture into a 10 to 12-inch cast-iron skillet or an 8x8-inch baking dish. Sprinkle the topping evenly over top.