Heat oven to 350°F. Spray bottom only of 13x9-inch pan with cooking spray.
In large bowl, beat sugars, buttermilk, oil, vanilla and eggs with electric mixer on low speed 20 to 30 seconds or until blended. Add remaining ingredients except apples and walnuts; beat on low speed about 1 minute or until blended. Stir in apples and walnuts. Spread batter in pan.
Bake 40 to 45 minutes or until toothpick inserted in center comes out clean. Cool in pan on cooling rack 1 hour.
1 Serving: Calories 240 (Calories from Fat 90); Total Fat 10g (Saturated Fat 1g, Trans Fat 0g); Cholesterol 20mg; Sodium 150mg; Total Carbohydrate 34g (Dietary Fiber 2g, Sugars 18g) % Daily Value Vitamin A 0%; Vitamin C 0%; Calcium 4%; Iron 8% Exchanges 1 Starch, 1 Other Carbohydrate, 2 Fat Carbohydrate Choices 2