Preheat oven to 350° F (175 degrees C). Grease and flour a 10 inch tube pan.
Mix cinnamon, 3/4 cup of sugar, & apples in a bowl; set aside. Combine flour, salt, & baking powder in a bowl. Beat eggs and 2 cups of sugar with an electric mixer until fluffy. Pour in the flour mixture alternately with the oil. Beat in orange juice & vanilla until smooth & thoroughly mixed. Pour half of the batter into prepared pan. Layer half the apples on top. Pour remaining batter over, then finish by topping with the rest of the apples.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 1 hour and 30 min. to 1 hour and 45 min. Cool in the pans for 10 minutes before removing to cool completely on a wire rack.