Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan.

In a large mixing bowl, combine the all-purpose flour, baking soda, salt, and ground cinnamon; whisk until blended.

Cream the unsalted butter and granulated sugar together using an electric mixer for about 2 minutes until light and fluffy.

Add eggs one at a time, mixing well after each, then stir in vanilla extract.

Gradually add the dry mixture to the wet ingredients, mixing until just combined.

Gently fold in the grated apples and walnuts, ensuring even distribution.

Pour the batter into the prepared pan and bake for 30-35 minutes until golden brown.

Let the cake cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.

While cooling, prepare the frosting by beating cream cheese and butter until smooth, then gradually add powdered sugar, adjusting with milk if needed.

Once the cake is cooled, frost generously and slice to serve.