Heat oven to 375°F. In medium bowl, combine baking soda and buttermilk; set aside. Spray 18 muffin cups with nonstick cooking spray or line with paper baking cups. In small bowl, combine macadamia nuts and 2 tablespoons brown sugar; set aside.
To buttermilk mixture, add 1/2 cup brown sugar, applesauce, pineapple, reserved 2 tablespoons pineapple liquid, oil, gingerroot and egg; mix well.
Lightly spoon flour into measuring cup; level off. In large bowl, combine all purpose flour, whole wheat flour, baking powder and salt; mix well. Add pineapple mixture; stir just until dry ingredients are moistened. Fill muffin cups 2/3 to 3/4 full. Sprinkle about 1 teaspoon nut mixture over batter in each cup.
Bake at 375°F. for 15 to 18 minutes or until golden brown and toothpick inserted in center comes out clean. Immediately remove from pan; cool slightly. Serve warm.