Prepare the cake mix according to the box directions to create a 9×13 cake. Once the cake is baked, remove it from the oven and let it cool in the pan for about 15 minutes.
While the cake is cooling, prepare the Jello mixture. In a heatproof bowl, dissolve the flavored gelatin in 1 cup of boiling water. Stir until the gelatin is completely dissolved.
Add ½ cup of cold water to the gelatin mixture and stir well.
Use a fork to poke holes all over the cooled cake.
Then, use a spoon or pastry brush to spoon the Jello mixture on top of the cake so it seeps into the holes.
Refrigerate the cake for 3-4 hours, so the Jello has time to set.
Then top the cake with Cool Whip and fresh berries if using and serve!
Notes
While these are the three main ingredients you will need, keep in mind the cake mix and Jello mix will require other ingredients. This may vary based on your cake mix brand, but this may include water, oil, eggs, or milk.
If you plan to turn your Jello poke cake into an easy flag cake, you will also need fresh strawberries and blueberries.
Jello poke cake can be stored covered in the refrigerator for 2-3 days after making.