Pre-heat oven to 350 degrees. To prepare the cake, mix 1/2 cup granulated sugar and the cinnamon in a small bowl. Mix the flour, baking powder and salt in a medium bowl. Whisk 2 cups granulated sugar, the oil, sour cream, eggs organge juice and vanilla in a large bowl until blended. Stir in the flour mixture. Pour half the batter into a greased and floured 12 cup nonstick bundt pan. Sprinkle half the apples over the batter. Sprinkle with half the walnuts and half the cinnamon-sugar. Spoon the remaining batter over the layers. Sprinkle with the remaining apples, walnuts and cinnamon-sugar. Bake at 350 degrees for 55 minutes. Conver the pan loosely with foil and bake for 30 minutes longer or until a cake tester inserted near the center comes out clean. Cool in the pan on a wire rack for 10 minutes. Loosen the edge from the side of the pan and invert onto a wire rack to cool completely. Remove to a cake plate and sprinkle with confectioners' sugar.
To prepare the sauce, bring the cream, brown sugar, corn syrup and butter to a boil in a heavy saucepan, stirring occasionally. Reduce the heat to medium-high. Boil for 8 minutes or until reduced to 2 cups, stirring occasionally. Whisk in the vanilla and cool.
To prepare the whipped cream, beat the whipping cream and brown sugar in a large mixing bowl until soft peaks form. Add the bourbon and beat until stiff peaks form.
To serve, cut the cake into slices and serve with the warm sauce and whipped cream.