Preheat oven to 400 F. Lightly grease a 2 quart baking dish (or 9×9-inch baking dish); set aside.
For the filling, stir together apples, cranberries, sugar, orange juice, flour, and orange zest in a medium bowl. Set aside while you prepare the topping.
For the topping, whisk together flour, sugar, baking powder, baking soda, and salt in a separate medium bowl.
2 cups all-purpose flour, ⅔ cup granulated sugar, 2 teaspoons baking powder, 1 teaspoon baking soda, ½ teaspoon salt
Cut butter into flour mixture until it forms large crumbs.
6 tablespoons cold salted butter
Stir buttermilk into crumbs to form dough.
1 ⅓ cups buttermilk
Drop dough evenly over filling, spreading slightly if necessary. The dough will spread a little as it bakes.
Sprinkle sugar over dough.
1 tablespoon raw sugar
Place the dish on a rimmed baking sheet.
Bake for about 30-40 minutes, or until the filling is bubbly and the topping is golden brown.
Notes
Apples: It’s important to use baking apples so that they don’t bake down to mush. Granny Smith and Honeycrisp are two common varieties of baking apple. It’s also important to thinly slice the apples so that they cook down and get tender.
Cranberries: I've only used fresh cranberries in this recipe. Dried cranberries won't work.
Sugar: The amount of sugar you choose to use for the filling will depend on how sweet you like your desserts and the type of apple you use. If you use a sweeter baker apple, like a Honeycrisp, you may want to use slightly less sugar.
Flour: To properly measure the flour either weigh it or sift or stir to break it up, lightly spoon into a measuring cup, and level. Avoid packing the flour as that will give you heavy, dry topping.