Preheat the oven to 350 degrees F (175 degrees C). Grease and flour a 10-inch Bundt or tube pan. Combine diced apples, 1 tablespoon white sugar, and 1 teaspoon cinnamon in a medium bowl; set aside. Sift together flour, baking powder, and salt; set aside.

Combine 2 cups white sugar, oil, orange juice, vanilla, and eggs in a large bowl; beat with an electric mixer at high speed until smooth. Stir in flour mixture. Fold in chopped walnuts.

Pour 1/3 of the batter into prepared pan. Sprinkle with 1/2 of the apple mixture. Alternate layers of batter and filling, ending with batter.

Bake in the preheated oven until a toothpick inserted into the center of cake comes out clean, about 55 to 60 minutes. Let cool in pan for 10 minutes, then turn out onto a wire rack and cool completely. Sprinkle with confectioners' sugar.