Toss sliced apples and walnuts with cinnamon and 1/2 cup sugar and set aside.
Stir dry ingredients together in a large mixing bowl.
In a separate bowl, whisk together oil, orange juice, 2 cups sugar and vanilla.
Mix wet ingredients into dry ingredients, then add eggs, one at a time. Beat just until smooth.
Pour half of batter into a greased and floured tube pan. Spread half of apples over it.
Pour the remaining batter over the apples and arrange the remaining apples on top.
Bake at 350 degrees for 1 1/4-1 1/2 hours. Cool before removing from pan.