Preheat the oven to the temperature specified on your cake mix box. Generously spray a 9×13-inch baking dish with cooking spray.
Prepare the cake batter according to package instructions. Pour into the greased dish and bake as directed. Let the cake cool for 15 minutes after baking.
Use the rounded end of a wooden spoon or a skewer to poke holes evenly across the cake, spacing them about 1 inch apart.
In a heatproof bowl, dissolve the strawberry gelatin in boiling water, stirring for 2 minutes. Add the cold water and mix well.
Slowly pour the gelatin mixture over the cake, letting it seep into the holes. Allow the cake to cool and absorb the gelatin for 1 hour.
In a bowl, mix together softened cream cheese, powdered sugar, and vanilla extract until smooth.
Gently fold in the whipped topping until fully combined.
Evenly spread the cheesecake mixture over the cooled cake and gelatin layer. Chill in the refrigerator for 4 to 6 hours to set.
Once set, spread the strawberry pie filling over the top of the cheesecake layer.
Garnish with fresh sliced strawberries, if using. Slice and serve chilled.