1. Preheat oven to 350 Degrees. Position rack in center of oven. Lightly grease 12 cup Bundt pan with cooking spray. 2. Whisk flour blend, baking powder, baking soda, buttermilk powder, cinnamon, xanthan gum, nutmeg, allspice and salt in a small bowl. Set aside. 3. Beat eggs in a large bowl of an electric mixer until well blended. Add white and brown sugars and beat until creamy, about one minute. Scrape the bowl and add the flour mixture, oil, rum, water and vanilla and mix at low speed for about one minute. (Do not overbeat.) then mix in apples and walnuts. 4. Spread batter into prepared Bundt pan. Place in center of preheated oven and bake for approx. 50-55 minutes or until toothpick inserted in center of cake comes out clean. (DO NOT OPEN OVEN DURING THE FIRST 45 MINUTES OF BAKING.) 5. Remove cake and cool on a rack for 8 minutes before carefully removing cake from the pan. Cool slightly on a rack. 6. Spoon Caramel Glaze over cake or simply dust with confectioners sugar. Cool completely.