oven to 350°F. Grease 2(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.
2. SPOON half of the white batter and half of the pink batter, side by side, into each prepared pan.
3. SWIRL batters together lightly, using a teaspoon. (Do not overswirl, or the color of the cake will be all pink and not pink and white marbled.) Bake 30 min. Cool 30 min. in pans. Remove to wire racks; cool completely.
4. MIX sour cream and powdered sugar in a medium bowl until well blended. Gently stir in whipped topping.
5. 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.
6. TOP with 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 leftover cake in refrigerator. Makes 16 servings, 1 slice each.