Preheat oven to 350°. Grease and flour two 8- or 9-inch round cake pans; set aside. Prepare cake batter as directed on package. Pour half of the batter into medium bowl. Add dry gelatin mix; stir until well blended. Spoon half of the white batter and half of the pink batter, side-by-side, into each prepared pan. Swirl batters together using a teaspoon. Bake 30 min. Cool 30 min. in pans. Remove to wire racks; cool completely.
Mix sour cream and powdered sugar in medium bowl until well blended. Gently stir in whipped topping. Place one of the cake layers on serving plate; spread top with 1 cup of the whipped topping mixture. Top with 1 cup of the strawberries and remaining cake layer. Spread top and side of cake with remaining whipped topping mixture. Top with remaining 1/2 cup strawberries just before serving. Store any leftover cake in refrigerator.
White and strawberry-flavored cakes are swirled together, baked, and then layered with fresh strawberries and a creamy topping.