Preheat oven to 350℉ (180℃)
Prepare a 9" or 10" tube cake pan by spraying with non-stick baking spray.
Combine flour, salt, baking powder and ground cinnamon in a bowl. Set aside for later.
3 Cups All-Purpose Flour, 1 teaspoon Salt, 1 Tablespoon Baking Powder, 2 teaspoons Ground Cinnamon
In a separate bowl, whisk together the granulated sugar, vegetable oil, vanilla, orange zest, and eggs until smooth and fully combined. Note - make sure eggs are fully incorporated.
1 Cup Vegetable Oil, 2 Cups Granulated Sugar, 1 Tablespoon Orange Zest, 1 teaspoon Pure Vanilla Extract, 4 Large Eggs
Add half of the dry ingredients to the mixing bowl. Use a spatula to stir until the mixture is smooth.
Stir in the orange juice.
2 Tablespoons Orange Juice
Add the remaining dry ingredients to the bowl and stir until smooth.
Pour ⅓ of the batter into the prepared tube cake pan and smooth with a spatula.
Sprinkle the apple and walnut mixture over the cake batter in the pan, then pour the remaining batter on top.
Bake for 60 - 65 minutes or until toothpick inserted in the center of the cake comes out clean.
Remove the cake from the oven and place it on a cooling rack for 15 minutes. Then invert the pan onto the rack and let the cake cool completely, leaving the pan on top.
Carefully lift cake pan off of cake and transfer to a serving platter.