Preheat oven to 350 degrees, grease a 9" x 13" baking dish with butter then set aside.
First, make the dough for the dumplings. Whisk together flour, baking powder, baking soda and salt in a large mixing bowl. Then, cut cold butter cubes into the mixture until butter chunks are the size of peas. Make a well in the center of the mixture then pour in buttermilk. Mix in buttermilk just until dry ingredients have been moistened.
Form dough into a cohesive ball then wrap with plastic wrap. Place dough in fridge or freezer for a few minutes to get nice and cold while you prepare the filling.
Next, peel, core then cut apples into ¼" pieces. As you cube each apple, place pieces into a mixing bowl, coat with the juice of ½ a lemon to prevent browning, then set aside.
Remove dough from the fridge or freezer. Roll it out slightly less than ¼" thick, into a 12" x 16" rectangle, then cut into 4" x 4" squares.
Drain excess liquid from chopped apples. Mix together the remaining lemon juice, cinnamon and salt. Drain the apples and add the juice mixture.
Place 2-3 Tbsp of apples into the center of each square. Bring each corner into the center of the square then pinch seams together, forming a pyramid-like shape. Place bundles, seam side down, into prepared casserole dish. Repeat with remaining apples and pastry squares. Once completed, set dish aside.
Melt butter over medium heat in a saucepan. Once the butter has melted, remove saucepan from the heat then stir in sugar, vanilla and nuts—the sugar will remain somewhat grainy. Divide sauce in half then pour half evenly over dumplings. Set remaining sauce aside.
Pour apple cider over each dumpling, making certain to coat each one. Sprinkle dumplings with ground cinnamon then bake 40-50 minutes—until the tops of the dumplings turn golden brown and are firm to the touch.
Let dumplings cool for at least 15 minutes. Spoon remaining sauce over each dumpling then serve warm or at room temperature. Enjoy!
One Last Thing
Apple dumplings taste great on their own, but they are even better served warm with a scoop of French vanilla ice cream!