Preheat oven to 350°F Lightly oil and flour the cake molds of a mini Bundt cake pan. In a medium sized mixing bowl, hand-mix the grated apples, 1 tablespoon sugar and cinnamon; set aside. In another bowl, sift the flour, baking powder and salt together; set aside.
In a larger bowl, combine 2 cups sugar, oil, orange juice, vanilla and eggs. Beat at a higher speed until contents are a smooth consistency. Stir in the flour mixture. If using chopped walnuts, fold them into the mixture during this step.
Stir the grated apples into the batter mixture. Pour the batter into each mini Bundt cake mold until full.
Bake in preheated oven for 50 minutes, or until the cake provides slight resistance when lightly touched. Let cakes cool in the pan for 10 minutes, then remove onto a wire rack until completely cool. Sprinkle tops of mini Bundt cakes with confectioners' sugar.