Preheat the oven to 350 degrees and spray a 9" x 13" baking pan with cooking spray.
In a large bowl mix the cake mix, lemon jello (dry), eggs, oil and water together for at least 2 minutes.
Bake cake as directed on the cake mix package. Test the cake with a toothpick for doneness.
Remove the cake from the oven and place on a wire rack. While cake is still hot, poke holes all over the top (I use a wooden skewer). You could also use a fork or a toothpick.
Mix lemon juice, powdered sugar and melted butter together in a small bowl. Pour the lemon mixture over the entire cake. Spread evenly with a spoon or spatula.
Let cake cool and serve as is or with a dollop of whipped cream or a scoop of vanilla ice cream.
If desired, you can grate a little lemon zest on top of the whipped cream to add extra lemon flavor.
Notes: *Cake can be made with a yellow cake (original recipe) or if you want even more lemony flavor, make it with a lemon cake mix. *Only use fresh lemon juice for the glaze. *Store cake covered at room temperature for 2-3 days. If you still have leftover cake place in the refrigerator. *Cake can be frozen in a freezer safe container for up to three months.