HEAT oven to 350°F. Spray a 13 x 9-inch baking pan with no-stick cooking spray.
COMBINE 3/4 cup frosting and 2 eggs; stir until smooth. Add cake mix; stir until blended and cake mix is moistened. Spread mixture in baking pan; top with remaining frosting. Bake 20 to 25 minutes or until toothpick inserted around the edge comes out clean. Remove from oven.
TOP cake with peach slices. Whisk together sour cream, remaining egg and vanilla until smooth. Pour evenly over peaches. Bake an additional 20 to 25 minutes or until the sour cream topping is set.
Serving Size (1/12 of recipe), Calories 410 (Calories from Fat 160), Total Fat 18g (Saturated Fat 8g, Trans Fat 2g), Cholesterol 60mg, Sodium 380mg, Total Carbohydrate 58g (Dietary Fiber 2g, Sugars 21g), Protein 4g; Percent Daily Value*: Vitamin A 6%, Vitamin C 2%, Calcium 8%, Iron 8%.
*Percent Daily Values are based on a 2,000 calorie diet.