Preheat your oven to 350°F and grease a 9x13-inch baking pan with butter or cooking spray. Line the bottom with parchment paper for easy removal once baked.
Whisk together flour, baking soda, salt, cinnamon, and nutmeg in a medium bowl. Set this dry mixture aside while you prepare the wet ingredients.
Beat softened butter and granulated sugar together until light and fluffy, about 3 minutes. Add eggs one at a time, beating well after each addition, then stir in vanilla extract.
Alternate adding the dry mixture and sour cream to the butter mixture, beginning and ending with dry ingredients. Fold in diced apples and apple cider gently until just combined—this fall apple cake crowd recipe depends on not overmixing.
Pour batter into the prepared pan and spread evenly. Toss walnuts with brown sugar and sprinkle over the top before baking.
Bake for 50 minutes until a toothpick inserted in the center comes out with just a few moist crumbs. The top should be golden brown and spring back when lightly touched.
Cool the apple cake crowd dessert in the pan for 15 minutes, then turn out onto a wire rack. Serve warm or at room temperature with whipped cream or vanilla ice cream.