You can find soy flour at your health food store or Whole Foods. If you can't find soy flour, just use 2 cups of all-purpose flour in place of the whole wheat pastry flour and soy flour.
Preheat oven to 350 degrees F. Spray a 9 x 13 pan with nonstick cooking spray. In a small bowl, whisk together flours, baking soda, spices and salt. In a large bowl, beat buttermilk and eggs together. Mix in pumpkin, sugars, oil, flaxseed meal, pineapple and carrots. Stir in walnuts. Mix in flour mixture a little at a time. Pour batter into prepared pan. Bake 30-35 minutes until a toothpick inserted in the center comes out clean.
Invert onto large board and cool completely. Frost with Cream Cheese Icing with Tofu.
Serves 24.
Per serving: 165 calories, 8 g fat (1 g saturated), 27 mg cholesterol, 21 g carbohydrate, 3 g fiber, 5 g protein, 41% Vitamin A, 3% Vitamin C, 6% calcium, 7% iron