While your cake is cooling, whisk the Jello mix into the boiling water in a glass measuring cup until completely dissolved.
Use a fork to poke holes about 1-2 inches apart all over the top of your lemon poke cake.*
Slowly pour the Jello mixture over the entire cake, and then let it cool for another 10-15 minutes.
While your cake is cooling, whisk together the powdered sugar and lemon juice in a small mixing bowl. This will be your lemon glaze.
Next, pour or spoon your lemon glaze all over the top of the cake, making sure to spread it evenly.
Finally, you'll want to let the cake fully cool before spreading Cool Whip or whipped cream all over the top with a spatula.
Once the Cool Whip is spread on top, I recommend chilling your lemon Jello poke cake in the refrigerator for at least a few hours before serving. This gives the lemon flavor time to infuse into the cake.
Once chilled, serve and enjoy your lemon poke cake with a sprinkling of lemon zest or even a slice of fresh lemon on top!